chore(guides): add raw json request guide

Signed-off-by: imdhemy <[email protected]>

guides/raw-request.md

@@ -0,0 +1,50 @@
+# Raw JSON Requests
+
+Opensearch client implements many high-level APIs out of the box. However, there are times when you need to send a raw
+JSON request to the server. This can be done using the `request()` method of the client.
+
+The `request()` method expects the following parameters:
+
+| Parameter     | Description                                                                  |
+|---------------|------------------------------------------------------------------------------|
+| `$method`     | The HTTP method to use for the request, `GET`, `POST`, `PUT`, `DELETE`, etc. |
+| `$uri`        | The URI to send the request to, e.g. `/_search`.                             |
+| `$attributes` | An array of request options. `body`, `params` & `options`                    |
+
+> ![NOTE]
+> The `request()` is a wrapper around the `\OpenSearch\Transport::performRequest()` method, this explains why [the
+> parameters](https://github.com/opensearch-project/opensearch-php/blob/bf9b9815e9636196295432baa9c0368bc2efadd8/src/OpenSearch/Transport.php#L99)
+> are intentionally similar.
+
+Most of the time, you will only need to provide the `body` attribute. The `body` attribute is the JSON payload to send
+to the server. The `params` attribute is used to set query parameters, and the `options` attribute is used to set
+additional request options.
+
+To send a raw JSON request you need to map the documentation to the `request()` method parameters. For example, [this
+request](https://opensearch.org/docs/2.12/search-plugins/keyword-search/#example) that query searches for the
+words `long live king` in the `shakespeare` index:
+
+```
+GET shakespeare/_search
+{
+  "query": {
+    "match": {
+      "text_entry": "long live king"
+    }
+  }
+}
+```
+
+Can be translated to the following `request()` method call:
+
+```php
+$response = $client->request('GET', '/shakespeare/_search', [
+    'body' => [
+        'query' => [
+            'match' => [
+                'text_entry' => 'long live king'
+            ]
+        ]
+    ]
+]);
+```