Add federationLink to groups

[JBWatenbergScality]

This PR adds support for a federationLink in the Groups, so that when retrieving the groups via the group-with-links new endpoints we know if it is a LDAP federated group or not.

It introduces 2 major things:

• A new LDAP group mapper provider ID that needs to be used to keep the reference of the Provider Id next to the group (so when creating the group mapper we need to mention providerId: group-with-link-ldap-mapper instead of. providerId: group-ldap-mapper)
• A new admin resource GET /admin/realms/master/groups-with-link that list groups apart with their federationLink if any is defined. The resource is searchable (thanks to the search query parameter and filterable per link to which we can provide the component id corresponding to the ldap integration component

[ChengYanJin]

This is amazing great work !