unify checking methods, fixes #2815

Closes #2815

Merge request studip/studip!1897

lib/classes/JsonApi/JsonApiIntegration/QueryChecker.php

@@ -104,16 +104,15 @@ class QueryChecker
 
     protected function checkSorting(ErrorCollection $errors, QueryParserInterface $queryParser): void
     {
-        $sorts = iterator_to_array($queryParser->getSorts());
-        if (null !== $sorts && null !== $this->sortParameters) {
-            foreach (array_keys($sorts) as $sortParameter) {
-                if (!array_key_exists($sortParameter, $this->sortParameters)) {
-                    $errors->addQueryParameterError(
-                        QueryParser::PARAM_SORT,
-                        sprintf('Sort parameter %s is not allowed.', $sortParameter)
-                    );
-                }
-            }
+        $withinAllowed = $this->keysWithinAllowed(
+            iterator_to_array($queryParser->getSorts()),
+            $this->sortParameters
+        );
+        if (!$withinAllowed) {
+            $errors->addQueryParameterError(
+                QueryParser::PARAM_SORT,
+                'Sort parameter should contain only allowed values.'
+            );
         }
     }