Define SDK only OpenAPI spec

[dabeeeenster]

So that we can see the canonical list of endpoints that are available to use by the SDKs.

Use tags (an example is used here https://github.com/axnsan12/drf-yasg/blob/b99306f71c6a5779b62189df7d9c1f5ea1c794ef/testproj/users/views.py#L19) to tag endpoints as SDK endpoints

[gagantrivedi]

As part of this, we should sure the data types are correct as well