[REQ] Add CancellationToken to list of arguments in Controller methods

Created by: philkild

Is your feature request related to a problem? Please describe.

I have a number of long-running server-side operations and handling cancellation from clients would be extremely useful. The ModelBinder will automatically bind RequestAborted to the cancellation token, therefore adding it as an argument is all that is required.

Describe the solution you'd like

Add a CancellationToken argument to all async calls.

Describe alternatives you've considered

I've tried to minimise long running calls and add caching but this would be a massive help.

Additional context

I found the following Blog post helpful.