[FEATURE] Make all decorators support async

[sdc50]

It looks like Django is trying to make their decorators handle both sync and async functions (see django/django#17621).

We should also try to do this with all of our decorators to give users the flexibility to write controllers, handlers, etc. as async coroutines.

[swainn]

Example that supports both sync and async is the with_paths decorator. Follow that pattern with other decorators. Good place to start is looking at the controller decorator and all of the decorators it uses/calls.