Refactor Options to subclass dict (#456)

`Options` is now pythonic. Even after subclassing dict, it retains attribute-style access.

This commit also contains:
- Remove `ContainerMeta` and replace with `__init_subclass__` in BaseContainer`
- Remove `BaseSerializer` functionality and associated files
- Object Model Documentation

docs/guides/compose-a-domain/register-elements.md

@@ -34,7 +34,7 @@ documentation to understand the additional options supported by that element.
 
 You can also choose to register elements manually.
 
-```python hl_lines="7-10 13"
+```python hl_lines="8-11 14"
 {! docs_src/guides/composing-a-domain/014.py !}
 ```
 

docs/guides/domain-definition/events.md

@@ -46,10 +46,30 @@ and where any delays occur.
 
 An event's metadata provides additional context about the event.
 
+Sample metadata from an event:
+
+```json
+{
+    "id": "test::user-411b2ceb-9513-45d7-9e03-bbc0846fae93-0",
+    "type": "Test.UserLoggedIn.v1",
+    "fqn": "tests.event.test_event_metadata.UserLoggedIn",
+    "kind": "EVENT",
+    "stream": "test::user-411b2ceb-9513-45d7-9e03-bbc0846fae93",
+    "origin_stream": null,
+    "timestamp": "2024-08-16 15:30:27.977101+00:00",
+    "version": "v1",
+    "sequence_id": "0",
+    "payload_hash": 2438879608558888394
+}
+```
+
 #### `id`
 
 The unique identifier of the event. The event ID is a structured string, of the
-format **<domain>.<aggregate>.<version>.<aggregate-id>.<sequence_id>**.
+format `<domain-name>::<aggregate-name>-<aggregate-id>-<sequence_id>`.
+
+The `id` value is simply an extension of the event's stream combined with the
+`sequence_id`. Read the section on `sequence_id` to understand possible values.
 
 #### `type`
 
@@ -58,31 +78,32 @@ For e.g. `Shipping.OrderShipped.v1`.
 
 #### `fqn`
 
-The fully qualified name of the event. This is used internally by Protean
-to resconstruct objects from messages.
+Internal. The fully qualified name of the event. This is used by Protean to
+resconstruct objects from messages.
 
 #### `kind`
 
-Represents the kind of object enclosed in an event store message. Value is
-`EVENT` for Events. `Metadata` class is shared between Events and Commands, so
-possible values are `EVENT` and `COMMAND`.
+Internal. Represents the kind of object enclosed in an event store message.
+Value is `EVENT` for Events. `Metadata` class is shared between Events and
+Commands, so possible values are `EVENT` and `COMMAND`.
 
 #### `stream`
 
-Name of the event stream. E.g. Stream `user-1234` encloses messages related to
-`User` aggregate with identity `1234`.
+Name of the event stream. E.g. Stream `auth::user-1234` encloses messages
+related to `User` aggregate in the `Auth` domain with identity `1234`.
 
 #### `origin_stream`
 
-Name of the stream that originated this event or command.
+Name of the stream that originated this event or command. `origin_stream` comes
+handy when correlating related events or understanding causality.
 
 #### `timestamp`
 
-The timestamp of event generation.
+The timestamp of event generation in ISO 8601 format.
 
 #### `version`
 
-The version of the event.
+The version of the event class used to generate the event.
 
 #### `sequence_id`
 
@@ -94,18 +115,26 @@ sequence ID of `1.1`, and the second update would have a sequence ID of `2.1`.
 If the next update generated two events, then the sequence ID of the second
 event would be `3.2`.
 
+If the aggregate is event-sourced, the `sequence_id` is a single integer of the
+position of the event in its stream.
+
 #### `payload_hash`
 
-The hash of the event's payload.
+The `payload_hash` serves as a unique fingerprint for the event's
+[payload](#payload). It is generated by hashing the stringified event payload
+json with sorted keys.
+
+`payload_hash` can be used to verify the integrity of the payload and in
+implementing idempotent operations.
 
 ## Payload
 
 The payload is a dictionary of key-value pairs that convey the information
 about the event.
 
-The payload is made available as the data in the event. If
-you want to extract just the payload, you can use the `payload` property
-of the event.
+The payload is made available as the body of the event, which also includes
+the event metadata. If you want to extract just the payload, you can use the
+`payload` property of the event.
 
 ```shell hl_lines="22 24-25"
 In [1]: user = User(id="1", email="<EMAIL>", name="<NAME>")
@@ -140,9 +169,10 @@ Out[6]: {'user_id': '1'}
 Because events serve as API contracts of an aggregate with the rest of the
 ecosystem, they are versioned to signal changes to contract.
 
-By default, events have a version of **v1**.
+Events have a default version of **v1**.
 
-You can specify a version with the `__version__` class attribute:
+You can override and customize the version with the `__version__` class
+attribute:
 
 ```python hl_lines="3"
 @domain.event(part_of=User)

docs/guides/object-model.md

@@ -1,69 +1,101 @@
 # Object Model
 
-DOCUMENTATION IN PROGRESS
+Domain elements in Protean have a common structure and share a few behavioral
+traits.
 
-A domain model in Protean is composed with various types of domain elements,
-all of which have a common structure and share a few behavioral traits. This
-document outlines generic aspects that apply to every domain element.
+## Meta Options
 
-## `Element` Base class
+Protean elements have a `meta_` attribute that holds the configuration options
+specified for the element. 
 
-`Element` is a base class inherited by all domain elements. Currently, it does
-not have any data structures or behavior associated with it.
+Options are passed as parameters to the element decorator:
 
-## Element Type
+```python hl_lines="7"
+{! docs_src/guides/composing-a-domain/021.py !}
+```
 
-<Element>.element_type
+```python
+In [1]: User.meta_
+Out[1]: 
+{'model': None,
+ 'stream_category': 'user',
+ 'auto_add_id_field': True,
+ 'fact_events': False,
+ 'abstract': False,
+ 'schema_name': 'user',
+ 'aggregate_cluster': User,
+ 'is_event_sourced': False,
+ 'provider': 'default'}
+```
 
-## Data Containers
+### `abstract`
 
-Protean provides data container elements, aligned with DDD principles to model
-a domain. These containers hold the data that represents the core concepts
-of the domain.
+`abstract` is a common meta attribute available on all elements. An element
+that is marked abstract cannot be instantiated.
 
-There are three primary data container elements in Protean:
+!!!note
+    Field orders are preserved in container elements.
 
-- Aggregates: The root element that represents a consistent and cohesive
-collection of related entities and value objects. Aggregates manage their
-own data consistency and lifecycle.
-- Entities: Unique and identifiable objects within your domain that have
-a distinct lifecycle and behavior. Entities can exist independently but
-are often part of an Aggregate.
-- Value Objects: Immutable objects that encapsulate a specific value or
-concept. They have no identity and provide a way to group related data
-without independent behavior.
+## Reflection
 
-### Reflection
+Protean provides reflection methods to explore container elements. Each of the
+below methods accept a element or an instance of one.
 
+### `has_fields`
 
+Returns `True` if the element encloses fields.
 
-## Metadata / Configuration Options
+### `fields`
 
-Additional options can be passed to a domain element in two ways:
+Return a tuple of fields in the element, both explicitly defined and internally
+added.
 
-- **`Meta` inner class**
+Raises `IncorrectUsageError` if called on non-container elements like
+Application Services or Command Handlers.
 
-You can specify options within a nested inner class called `Meta`:
+### `declared_fields`
 
-```python hl_lines="13-14"
-{! docs_src/guides/composing-a-domain/020.py !}
-```
+Return a tuple of the explicitly declared fields.
 
-- **Decorator Parameters**
+### `data_fields`
 
-You can also pass options as parameters to the decorator:
+Return a tuple describing the data fields in this element. Does not include
+metadata.
 
-```python hl_lines="7"
-{! docs_src/guides/composing-a-domain/021.py !}
-```
+Raises `IncorrectUsageError` if called on non-container elements like
+Application Services or Command Handlers.
 
+### `has_association_fields`
 
-### `abstract`
+Returns `True` if element contains associations.
+
+### `association_fields`
+
+Return a tuple of the association fields.
+
+Raises `IncorrectUsageError` if called on non-container elements.
+
+### `id_field`
+
+Return the identity field of this element, or `None` if there is no identity
+field.
+
+### `has_id_field`
+
+Returns `True` if the element has an identity field.
+
+### `attributes`
+
+Internal. Returns a dictionary of fields that generate a representation of
+data for external use.
+
+Attributes include simple field representations of complex fields like
+value objects and associations.
 
+Raises `IncorrectUsageError` if called on non-container elements
 
-### `auto_add_id_field`
+### `unique_fields`
 
+Return fields marked as unique.
 
-Abstract elements:
-Most elements can be marked abstract to be subclassed. They cannot be instantiated
-, but their field orders are preserved. Ex. Events.
+Raises `IncorrectUsageError` if called on non-container elements.

docs_src/guides/composing-a-domain/014.py

@@ -1,4 +1,5 @@
-from protean import BaseAggregate, Domain
+from protean.core.aggregate import BaseAggregate
+from protean.domain import Domain
 from protean.fields import Integer, String
 
 domain = Domain(__file__, load_toml=False)
@@ -10,4 +11,4 @@ class User(BaseAggregate):
     age = Integer()
 
 
-domain.register(User, stream_name="account")
+domain.register(User, stream_category="account")

docs_src/guides/composing-a-domain/015.py

@@ -4,7 +4,7 @@
 domain = Domain(__file__, load_toml=False)
 
 
-@domain.aggregate(stream_name="account")
+@domain.aggregate(stream_category="account")
 class User:
     first_name = String(max_length=50)
     last_name = String(max_length=50)

docs_src/guides/composing-a-domain/020.py

@@ -4,14 +4,11 @@
 domain = Domain(__file__, load_toml=False)
 
 
-@domain.aggregate
+@domain.aggregate(stream_category="account")
 class User:
     first_name = String(max_length=50)
     last_name = String(max_length=50)
     age = Integer()
 
-    class Meta:
-        stream_name = "account"
-
 
 domain.register(User)

docs_src/guides/composing-a-domain/021.py

@@ -4,7 +4,7 @@
 domain = Domain(__file__, load_toml=False)
 
 
-@domain.aggregate(stream_name="account")
+@domain.aggregate(stream_category="account")
 class User:
     first_name = String(max_length=50)
     last_name = String(max_length=50)

docs_src/guides/consume-state/001.py

@@ -39,7 +39,7 @@ class Inventory:
     in_stock = Integer(required=True)
 
 
-@domain.event_handler(part_of=Inventory, stream_name="order")
+@domain.event_handler(part_of=Inventory, stream_category="order")
 class ManageInventory:
     @handle(OrderShipped)
     def reduce_stock_level(self, event: OrderShipped):

docs_src/guides/consume-state/002.py

@@ -110,7 +110,7 @@ def adjust_stock(self, command: AdjustStock):
         repository.add(product)
 
 
-@domain.event_handler(stream_name="product")
+@domain.event_handler(stream_category="product")
 class SyncInventory:
     @handle(ProductAdded)
     def on_product_added(self, event: ProductAdded):

mkdocs.yml

@@ -144,10 +144,13 @@ nav:
         - guides/domain-behavior/aggregate-mutation.md
         - guides/domain-behavior/raising-events.md
         - guides/domain-behavior/domain-services.md
+
+    - Foundation:
       - guides/object-model.md
       - guides/identity.md
-    - App Layer:
       - guides/configuration.md
+
+    - App Layer:
       - Changing State:
         - guides/change-state/index.md
         - guides/change-state/commands.md