Organize response bodies into package and modules

[andrewvillazon]

The response bodies used for tests are becoming unruly and need to be organized into a package with modules. Something like:

tests/
└── fixtures/
    ├── __init__.py
    └── responsebodies/
        ├── __init__.py
        ├── admin.py
        ├── apps.py
        ├── dashboards.py
        ├── dataflows.py
        ├── groups.py
        └── etc...