Add the ability to get the all searchable keys

Author: Torann

src/Repositories/AbstractRepository.php

@@ -287,6 +287,18 @@ public function orderBy($column, $direction)
         });
     }
 
+    /**
+     * Return searchable keys.
+     *
+     * @return array
+     */
+    public function getSearchableKeys()
+    {
+        return array_values(array_map(function($value, $key) {
+            return is_array($value) ? $key : $value;
+        }, $this->searchable, array_keys($this->searchable)));
+    }
+
     /**
      * Filter results by given query params.
      *