Add implementation for DELETE /users/:userId/saved-opportunities/:oppId

[chouinar]

Summary

This endpoint should follow the standard pattern for our API endpoints. We should put the business logic in a separate service file, the API implementation itself should be as simple as shown below.

... other decorators
@user_blueprint.auth_required(api_jwt_auth)
@flask_db.with_db_session()
def my_endpoint(db_session: db.Session, user_id) -> response.ApiResponse:
     user_token_session: UserTokenSession = api_jwt_auth.current_user  # type: ignore

     if user_token_session.user_id != user_id:
           raise_flask_error(401, "Unauthorized user)

     with db_session.begin():
          data = some_function_in_service_file(db_session, user_id)

     return response.ApiResponse("Success", data=data)    

Acceptance criteria

• Error if the user_id of the authenticated user does not match the one from the path (only a user can access their own data)
• Error if the record does not exist in the table (404)
• Deletes the record
• Unit tests added for error cases and happy cases

[mikehgrantsgov]

This is covered in PR 3358