Save chat conversations via REST API

Is there any way to save the chat conversations?

I am using an architecture as below.

Client : ASP.NET SignalR JavaScript Library v2.0.0
Server side : Microsoft.AspNet.SignalR.Hubs(To communicate with client) + Matrix Library(To communicate with
open fire using XMPP Client)
Database : SqlServer

I want to know if openfire has any Service/API to save chat conversation.

I am using openfire 4.2.1. I have downloaded the REST API plugin. I could create/update/delete/search user and group. I want to know how to add users to group.

There is an API to add users to group.


But to which group the user will be added.

Open fire shows the details about the client sessions.

Also please let me know how group chat can be achieved. I checked the below link,

But, I could not get more details about group chat.

Thanks & Regards,
Anoop H.N.