[mercedesme] Refactor code and fix test (openhab#16897)

Also-by: Bernd Weymann <[email protected]>
Signed-off-by: Leo Siepel <[email protected]>

Author: lsiepel

bundles/org.openhab.binding.mercedesme/src/main/java/org/openhab/binding/mercedesme/internal/handler/AccountHandler.java

@@ -227,7 +227,7 @@ public void onAccessTokenResponse(AccessTokenResponse tokenResponse) {
             // all failed - start manual authorization
             String textKey = Constants.STATUS_TEXT_PREFIX + thing.getThingTypeUID().getId()
                     + Constants.STATUS_AUTH_NEEDED;
-            updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.NONE,
+            updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.COMMUNICATION_ERROR,
                     textKey + " [\"" + thing.getProperties().get("callbackUrl") + "\"]");
         }
     }