(Improvement) Support custom actions via ActionAPI

[stevelacey]

Support custom actions via PUT requests that proxy to model or view methods.

1. Inherit ActionAPI in the view
2. Define some actions on the view (a list of strings)
3. Register the action route (last, it's wildcard)

path("profiles/<uuid:id>/", views.ProfileDetail.as_view()),
path("profiles/<uuid:id>/<str:action>/", views.ProfileDetail.as_view()),

ActionAPI will call a corresponding view method if one exists, this is handy if more complex validation needs to happen before the action is run, otherwise, the model method is called directly.

The bundle and request.user are passed through via kwargs to the action be it a model or view action, primarily this is so that model actions can store the user acting upon the instance.

Action names are defined in snake_case but passing kebab-case via the URL is supported.

ActionAPI can be used with or without DetailAPI and UpdateAPI.