[10.x] Add forbid, forbid_if and forbid_unless helpers

[karkowg]

Small nicety on top of abort, abort_if and abort_unless but dedicated to throwing unauthorized exceptions (403).

forbid('You shall not pass!');

[milwad-dev]

I don't agree

[driesvints]

@milwad-dev instead of saying "I don't agree" please state your reasoning.

[morloderex]

@karkowg wouldn't it be better to use throw_if and throw_unless for this, and then just throw the Illuminate\Auth\Access\AuthorizationException?

My reasoning is that Illuminate\Auth\Access\AuthorizationException's underlying response could have been modified and just by using the abort_if and abort_unless helpers respectively we are by-passing this customisation?

[taylorotwell]

I honestly don't mind this method but fear it opens the door to a PR for every single status code imaginable. 😅

[taylorotwell]

Feel free to define in your own project. 👍