Implement XEP-0333 Chat Markers
Submitted by Ferdinand Stehle
Assigned to Telepathy bugs list
Description
https://xmpp.org/extensions/xep-0333.html
In comparison to XEP-0184 Message Receipts, chat markers enable additional feedback like "displayed" and "acknowledged".
Together with XEP-0280 Message Carbons, the forwarded "displayed" marker of ones client can be utilized to remove notifications on other available resources.