Feature dmf target delete aware (#474)

* Implemented new function to create and send a thing created message if a
delete event is published

- added mock and integration tests 

Signed-off-by: Jonathan Philip Knoblauch <JonathanPhilip.Knoblauch@bosch-si.com>

* Switched target address form URI to String and fixed test

Signed-off-by: Jonathan Philip Knoblauch <JonathanPhilip.Knoblauch@bosch-si.com>

* Refactoring and removed TODOs

Signed-off-by: Jonathan Philip Knoblauch <JonathanPhilip.Knoblauch@bosch-si.com>

* Fixed javadoc and description

Signed-off-by: Jonathan Philip Knoblauch <JonathanPhilip.Knoblauch@bosch-si.com>

* Used Target from API instead from JpaTarget 

Signed-off-by: Jonathan Philip Knoblauch <JonathanPhilip.Knoblauch@bosch-si.com>

* Refactoring after review

Signed-off-by: Jonathan Philip Knoblauch <JonathanPhilip.Knoblauch@bosch-si.com>

* Small refactoring - fixed typos

Signed-off-by: Jonathan Philip Knoblauch <JonathanPhilip.Knoblauch@bosch-si.com>

* Resolve Merge conflicts

Signed-off-by: Melanie Retter <melanie.retter@bosch-si.com>

hawkbit-dmf-api/src/main/java/org/eclipse/hawkbit/dmf/amqp/api/MessageType.java

@@ -10,8 +10,6 @@ package org.eclipse.hawkbit.dmf.amqp.api;
 
 /**
  * The amqp message types which can be handled.
- * 
- *
  *
  */
 public enum MessageType {
@@ -22,8 +20,13 @@ public enum MessageType {
     EVENT,
 
     /**
-     * the thing created type.
+     * The thing created type.
      */
     THING_CREATED,
 
+    /**
+     * The thing deleted type.
+     */
+    THING_DELETED,
+
 }