Support hardcoded-ldap-group-mapper LDAP Mapper

[cthiebault]

This would grant a specified Keycloak group to each Keycloak user linked with LDAP.
See documentation

It could look like this:

resource "keycloak_ldap_hardcoded_group_mapper" "group_mapper" {
  realm_id                 = "${keycloak_realm.my-realm.id}"
  ldap_user_federation_id  = "${keycloak_ldap_user_federation.my-ldap.id}"
  name                     = "my-group-mapper"
  group                    = "my-group"
}

[mrparkers]

Closed via #264.