EX should not try to show history in for a new member of an existing encrypted room

[pmaier1]

Story

Currently there is no room history key sharing functionality available in EX. This feature will be added at a later point in time. Therefore the app should not attempt to show historical messages when a new user joins a room.

Steps to reproduce

1. Alice creates an e2ee room
2. Normal room activity takes place
3. Bob joins the room (simple join or invite)

Expected behavior

• Bob gets informed that he cannot read history in this room (similar to how the missing key backup functionality is handled)

Actual behavior

• Bob receives historical messages but all of them are UTDs (which is expected as he cannot get the keys for them)

Related

• Missing events received before accepting room invite element-x-ios#1240

@manuroe @VolkerJunginger

[ara4n]

N.B. that you might still have the keys (e.g. if the non-EX client who invited you sent you the keys preemptively), so you should only hide the messages if empirically you don't have keys to decrypt them.

[pmaier1]

This is being handled as part of the current work on hiding expected UTDs #2312.