LdapUserBackend: Unfold the user_name_attribute automatically

This is.. the currently easiest solution. As long as attribute unfolding
is not very performance intensive this solution suffices.

refs #10367
refs #10332

library/Icinga/Authentication/User/LdapUserBackend.php

@@ -341,6 +341,27 @@ class LdapUserBackend extends LdapRepository implements UserBackendInterface, In
         return $table;
     }
 
+    /**
+     * Validate that the given column is a valid query target and return it or the actual name if it's an alias
+     *
+     * @param   string              $table  The table where to look for the column or alias
+     * @param   string              $name   The name or alias of the column to validate
+     * @param   RepositoryQuery     $query  An optional query to pass as context
+     *
+     * @return  string                      The given column's name
+     *
+     * @throws  QueryException              In case the given column is not a valid query column
+     */
+    public function requireQueryColumn($table, $name, RepositoryQuery $query = null)
+    {
+        $column = parent::requireQueryColumn($table, $name, $query);
+        if ($name === 'user_name' && $query !== null) {
+            $query->getQuery()->setUnfoldAttribute('user_name');
+        }
+
+        return $column;
+    }
+
     /**
      * Authenticate the given user
      *