Introduce target grouping (#2538)

* Introduce target grouping

Signed-off-by: strailov <Stanislav.Trailov@bosch.io>

* minor refactor

Signed-off-by: strailov <Stanislav.Trailov@bosch.io>

* throw validation exception instead direct returning bad request response

Signed-off-by: strailov <Stanislav.Trailov@bosch.io>

* fix group query parameter

Signed-off-by: strailov <Stanislav.Trailov@bosch.io>

* remove wrongly added import

Signed-off-by: strailov <Stanislav.Trailov@bosch.io>

* add review fixes

Signed-off-by: strailov <Stanislav.Trailov@bosch.io>

* apply latest review changes

Signed-off-by: strailov <Stanislav.Trailov@bosch.io>

* apply latest changes after sybnc/review

Signed-off-by: strailov <Stanislav.Trailov@bosch.io>

* fix after review

Signed-off-by: strailov <Stanislav.Trailov@bosch.io>

---------

Signed-off-by: strailov <Stanislav.Trailov@bosch.io>

hawkbit-core/src/main/java/org/eclipse/hawkbit/repository/TargetFields.java

@@ -29,6 +29,7 @@ public enum TargetFields implements RsqlQueryField {
     UPDATESTATUS("updateStatus"),
     IPADDRESS("address"),
     ATTRIBUTE("controllerAttributes"),
+    GROUP("group"),
     ASSIGNEDDS(
             "assignedDistributionSet",
             DistributionSetFields.NAME.getJpaEntityFieldName(), DistributionSetFields.VERSION.getJpaEntityFieldName()),