How can the server send persistent messages to groups?

Hi, what is the preferred way for server to send chat messages into group channels?

Case in point we want the server to send message into group channels for people finishing tournament on rank 1,2,3.

From what Chris discussed in the gitter, it could achieved by using nk.StreamSendRaw, but in case the message needs to be persistent we need to write to database directly, how can this be achieved?