Use fromRawAttributes() for custom pivot models (#184)

Fixes wintercms/winter#741. Related: wintercms/wn-test-plugin#11

src/Database/Model.php

@@ -853,7 +853,7 @@ public function newRelationPivot($relationName, $parent, $attributes, $table, $e
 
         if (!is_null($definition) && array_key_exists('pivotModel', $definition)) {
             $pivotModel = $definition['pivotModel'];
-            return $pivotModel::fromAttributes($parent, $attributes, $table, $exists);
+            return $pivotModel::fromRawAttributes($parent, $attributes, $table, $exists);
         }
     }