Revert "(mvc) unused, pull part of https://github.com/opnsense/core/pull/1134"

When working on another plugin, I remembered why this was usefull ;)

This reverts commit e55feb1e.

src/opnsense/mvc/app/controllers/OPNsense/Base/ApiMutableModelControllerBase.php

@@ -106,6 +106,22 @@ abstract class ApiMutableModelControllerBase extends ApiControllerBase
         return $this->modelHandle;
     }
 
+    /**
+     * validate and save model after update or insertion.
+     * Use the reference node and tag to rename validation output for a specific node to a new offset, which makes
+     * it easier to reference specific uuids without having to use them in the frontend descriptions.
+     * @param $node reference node, to use as relative offset
+     * @return array result / validation output
+     */
+    protected function validateAndSave($node = null)
+    {
+        $result = $this->validate();
+        if (empty($result['result'])) {
+            return $this->save();
+        }
+        return $result;
+    }
+
     /**
      * validate this model
      * @param $node reference node, to use as relative offset