Story: Rather than having to assign each individual user within the RESTRICTED_USERS_WHITELIST, we would like to be able to configure this by LDAP groups

Background: For large organizations, having to manage each individual user within the RESTRICTED_USERS_WHITELIST is not feasible when dealing with hundreds of users. Allowing a field where users within particular groups from LDAP can also be configured with these permissions is much more easier to manage for a Quay administrator.

Acceptance criteria:

• Allow RESTRICTED_USERS_WHITELIST to accept groups as well as individual users
  OR
• Allow additional criteria for FEATURE_RESTRICTED_USERS to use groups, like a field called RESTRICTED_GROUPS_WHITELIST