OZG-5156 Code cleanup for review

* changed Unit Test to assertJ
* Moved config to Class

fim-adapter/src/main/java/de/ozgcloud/eingang/fim/FimService.java

@@ -24,10 +24,10 @@ public class FimService {
     public static final String UNKNOWN_SCHEME_NAME = "unknown";
 
     @Autowired
-    private final FimConfig fimConfig = null;
+    private FimConfig fimConfig;
 
     @Autowired
-    private final FimDataMapper fimDataMapper = null;
+    private FimDataMapper fimDataMapper;
 
     @Autowired
     private final List<FimSchemeAdapter> fimSchemeAdapters = new ArrayList<>();