Refactor OAuthAuthorizationGrant into classes with specific grant behavior

[Avery-Dunn]

Removal of dependencies in #926 has resulted in OAuthAuthorizationGrant taking on the responsibilities of every removed grant class.

This was done to reduce the complexity of the changes when removing nimbus, however it goes against OOP principles and long-term this will be hard to maintain.

That class should be split into classes that control grant-specific behavior, similar to the old imported classes.