Fix sonar issues and add DMF tests for maintenance window feature (#655)

* Fix sonar issues.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* POM cleanup and more sonar issues fixed.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Remove unneeded JavaDocs.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* More sonar issues.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* More issues.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Adapt maintenance window to naming.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Add DMF tests.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Readibility.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

* Typos fixed.

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

hawkbit-repository/hawkbit-repository-api/pom.xml

@@ -50,7 +50,6 @@
       <dependency>
          <groupId>com.cronutils</groupId>
          <artifactId>cron-utils</artifactId>
-         <version>5.0.5</version>
       </dependency>
 
       <!-- TEST -->