[LDAP Plugin] Support group / role mapping

It would be very nice if the LDAP Plugin could support mapping of LDAP Groups into PeerTube roles.

For instance:

• ou=Groups
  • cn=peertube-admin : mapped to PeerTube Administrator
  • cn=peertube-moderator : mapped to PeerTube Moderator
  • cn=peertube-user : mapped to PeerTube User

Of course, all those mappings should be editable as settings.

If this feature is enable, this could even provide a security to prevent LDAP users who aren't in any PeerTube LDAP Group to create an account.

I know this is more a feature request, but I did not find another location to report this.