- Currently ACL auth by default does username and password validation with ACL entries. We compose it with an IAuthenticator instance to inject authentication behavior of username and  password and then just validate the permissions against the ACL list of the user. This approach is more favorable as it minimizes changes and avoids redundant code needed to combine behaviors of AclAuthenticator and AADAuthenticator. Rather than inheriting these behavior, we compose AclAuthenticator with an IAuthenticator.

Testing:
There were no AAD tests. Have added a basic test to validate AAD + ACL and that it works with cluster auth.

- Refactor to AclWithAad and AclWithPassword hierarchies
- fix naming convention for private member _validateUsername
- add comments and fix tests

- Add support for groupId check and corresponding test

… and move test constructor for IssuerSigningTokenProvider to test code