I've implemented support for this feature in branch mam2-ext in the following projects:

• tigase-server
• tigase-message-archiving
• tigase-pubsub
• tigase-mix
• tigase-mongodb (MA & PubSub)
• tigase-tts-ng (test cases)

We do not have support for MAM2 in MUC and as far as I can see, MUC is not using UUID for stable-id nor it is keeping a separate column for stable-id. That makes it impossible to support MAM2 as we cannot search using stable-id. Due to that (and knowing that would be a bigger change, I would suggest leaving it as it is, and if desired address this "issue" in the next major version of Tigase XMPP Server.

@wojtek Please review those changes as they are quite big and may be changing API. I've tried to make sure that we will not break API with those changes but it would be good to review and confirm that and implementation of this new feature.

I went over the changes, especially regarding the API and I think they look ok and can be merged. There is not breaking of API per-se as everything still follows the interface or sub-class so even if someone was using the interface then it should still work thus it can be included in "minor" version.

Please do merge those changes.

All tests on TTS-NG related to MAM2#extended have passed, so I think we can assume that this is implemented and ready to be used.