fix: mail address handling in GUI after #1793

the referenced PR refactored the data structure. as a consequence, the path of the recipients field changed.
therefore, the web UI was displaying all emails in one line with commas in-between instead of one email per line.
this is because BatchInsertConverter was applied "recipients" which does not exist anymore.
it should be "mailSettings.recipients".

Author: goekay

src/main/java/de/rwth/idsg/steve/web/GlobalControllerAdvice.java

@@ -50,7 +50,7 @@ public void binder(WebDataBinder binder) {
         binder.registerCustomEditor(ChargePointSelect.class, new ChargePointSelectEditor());
 
         binder.registerCustomEditor(List.class, "idList", batchInsertConverter);
-        binder.registerCustomEditor(List.class, "recipients", batchInsertConverter);
+        binder.registerCustomEditor(List.class, "mailSettings.recipients", batchInsertConverter);
     }
 
     @ExceptionHandler(Exception.class)