code: func (api *PublicWhisperAPI) MarkTrustedPeer(ctx context.Context, url string) (bool, error) {
  	n, err := enode.ParseV4(url)
  	if err != nil {
  		return false, err
  	}
  	return true, api.w.AllowP2PMessagesFromPeer(n.ID().Bytes())
  }
docs: // MarkTrustedPeer marks a peer trusted, which will allow it to send historic (expired) messages.
  // Note: This function is not adding new nodes, the node needs to exists as a peer.