[11.x] Allow using custom authorization validator

[hafezdivandari]

Oauth2 Server allows passing a custom authorization validator (instance of AuthorizationValidatorInterface) to the constructor of ResourceServer class or pass null to use the default BearerTokenValidator.

Devs usually override BearerTokenValidator class to add additional params to the request when validating the token with custom claims, e.g. as this PR intends to make this easier:

• https://github.com/thephpleague/oauth2-server/pull/851

Or as mentioned here:

• https://github.com/thephpleague/oauth2-server/issues/885#issuecomment-708501516

This PR allows using custom authorization validator.

[taylorotwell]

I'm getting a bit weary of all the Passport deep customization PRs.

[parallels999]

I really need this 😢