fix(api): register responses with apispec using components.response() (#1881)
fix(api): register responses with apispec using components.response() (#1881)

responses should be registered with apispec using components.response();
not by directly modifying the _reponses dict, which is internal to the
ApiSpec.Components class.

Also, handle duplicate response registrations gracefully.

dpgaspar/Flask-AppBuilder,dpgaspar/Flask-AppBuilder,dpgaspar/Flask-AppBuilder,dpgaspar/Flask-AppBuilder