Add property for default message archiving in group chats
From https://github.com/xsf/xmpp-providers-website/issues/66:
I think it is important to have group history in public channels, which is known as MUC MAM in XMPP jargon. In my experience, the listed sure.im provider does not have this feature.
Even though https://compliance.conversations.im/server/sure.im/ shows it support muc mam, we noticed rooms created on the server did not have this working.