db constraint with unique remoteId if set, handle sync with tests

src/Bundle/ChillCalendarBundle/RemoteCalendar/Connector/MSGraph/RemoteEventConverter.php

@@ -31,7 +31,7 @@ class RemoteEventConverter
 {
     /**
      * valid when the remote string contains also a timezone, like in
-     * lastModifiedDate
+     * lastModifiedDate.
      */
     public const REMOTE_DATETIMEZONE_FORMAT = 'Y-m-d\\TH:i:s.u?P';