Better DI For controllers - Action parameter injection

[yishaigalatzer]

No description provided.

[tugberkugurlu]

I guess this means that we won't need custom parameter binding for things like IPrincipal, CancellationToken, etc. for actions, correct?

[pranavkm]

Related to #454

[pranavkm]

@tugberkugurlu quick feedback -

IPrincipal does not need to be injected it's directly supported from the Context now. Do you feel we need to support explicitly injecting it as a property and action parameter? We think not, but we are open to hearing a compelling argument :)

See controller code: https://github.com/aspnet/Mvc/blob/dev/src/Microsoft.AspNet.Mvc.Core/Controller.cs#L41-L52

We can look at CancellationToken but we need to figure out what to do about them top level. See #743

[pranavkm]

This is being tracked via #801.