Refactor hawkbit core and security (#2833)

* Refactor hawkbit core and security

* improve access to the base core features - static
* thus easiear access
* and less boilerplate passing of instances

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

* Refactor context classes

* make JSON context serialization default

* AccessContext

* Split hawkbit-security-core to other modules and remove it

---------

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

hawkbit-dmf/hawkbit-dmf-rabbitmq-test/src/main/java/org/eclipse/hawkbit/rabbitmq/test/AmqpTestConfiguration.java

@@ -14,7 +14,6 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 
-import org.eclipse.hawkbit.repository.helper.SystemSecurityContextHolder;
 import org.springframework.amqp.rabbit.connection.ConnectionFactory;
 import org.springframework.amqp.rabbit.core.RabbitTemplate;
 import org.springframework.amqp.support.converter.Jackson2JsonMessageConverter;
@@ -39,11 +38,6 @@ public class AmqpTestConfiguration {
         return rabbitTemplate;
     }
 
-    @Bean
-    SystemSecurityContextHolder systemSecurityContextHolder() {
-        return SystemSecurityContextHolder.getInstance();
-    }
-
     @Bean
     Executor asyncExecutor() {
         return new DelegatingSecurityContextExecutorService(Executors.newSingleThreadExecutor());