remove fastapi_responses, add manual additional responses docs

[govfvck]

The fastapi_responses library is not maintained anymore and does not find additional responses (HTTPException) correctly, and some of the responses are not documented very well in the autogenerated docs.

• removed fastapi_responses
• add app/utils/responses.py to add aditional responses models.
• add additional responses to the route operations to be included in the autogenerated docs.

for example create_admin route:

Before:

After:

I think this a good solution for now, so we could find a better way (maybe automatic) for this.