public function make_admin(string $id_chat, string $id_user): bool
  {
    if ( $this->is_admin($id_chat) ){
      return (bool)$this->db->update_ignore('bbn_chats_users', [
        'admin' => 1
      ], [
        'id_chat' => $id_chat,
        'id_user' => $id_user,
      ]);
    }
    return false;
  }