[11.x] Fix getting/setting client scopes and grant types

[axlon]

This PR fixes #1716:

As of version 11.10.2 it is no longer possible to get or set $scopes or $grant_types on the client model, due to changes made to it in #1709 and #1705.

I think this is because the added getters and setters do not respect the casts for these attributes that were already on the model.

Additionally, this PR introduces a new hasGrantType method on the client model, similar to the hasScope method it already has.

If this is merged I plan to create a second PR against master to have both of these methods return true by default, and remove the relevant casts.
This then gives developers full control over how they want to implement these methods by simply extending the client model. The skipsAuthorization() method already works this way and (IMO) this is great way to do things.

[axlon]

If this is merged I plan to create a second PR against master to have both of these methods return true by default, and remove the relevant casts.
This then gives developers full control over how they want to implement these methods by simply extending the client model. The skipsAuthorization() method already works this way and (IMO) this is great way to do things.

I've decided against trying this because the logic for hasScope() is a little bit more complex (currently) and would be annoying to maintain from outside Passport