[#1509] Sync Target type with SW and DS types / getByKey (Mgmt Layer) (#1516)

Signed-off-by: Marinov Avgustin <Avgustin.Marinov@bosch.com>

hawkbit-repository/hawkbit-repository-api/src/main/java/org/eclipse/hawkbit/repository/TargetTypeManagement.java

@@ -32,6 +32,14 @@ import org.springframework.security.access.prepost.PreAuthorize;
  */
 public interface TargetTypeManagement {
 
+    /**
+     * @param key
+     *            as {@link TargetType#getKey()}
+     * @return {@link TargetType}
+     */
+    @PreAuthorize(SpPermission.SpringEvalExpressions.HAS_AUTH_READ_TARGET)
+    Optional<TargetType> getByKey(@NotEmpty String key);
+
     /**
      * @param name
      *            as {@link TargetType#getName()}