Support XEP-0430: Inbox

[nesium]

In order to have unread indicators that are synchronized between multiple devices we should support XEP-0430.

This also affects prose-im/prose-core-client#44 where the use of Chat Markers should be modified and not removed to indicate to the server that messages have been read as outlined in XEP-0430.

Edit: I couldn't find an existing module for Prosody but ejabberd seems to support it.

[nesium]

I believe that the Inbox XEP wouldn't work with MUC unless something like MucSub is involved.

And even then, the idea that for each message every participant sends a read receipt and these need to be loaded from MAM again when paging through a conversation 😵‍💫

Although maybe the server just processes the receipt but doesn't save it to MAM, that would make sense.

[nesium]

We'd also need a method to mark a whole conversation as read without sending read markers for all (potentially very old) unread messages. The XEP mentions something like…

Unmarking a conversation always sets the unread counter to zero, and by implication sets all messages to be read.

But doesn't seem to show any example.