[Story] Show if a room has unread messages & mark room as "read"

[VolkerJunginger]

As a user that has unread messages I want to see which rooms have unread messages in the room list so I have fast access to read them.

• Show an indicator for room with unread message in the room-cell in the room list
• Mark the room as "read" when the user has oppened the room.
• • This is independent from the read status of the messages in the room
• • If a room has unread messages in a Thread still mark the room as read.

Remark
The indicator is more a "hint" for the user that there is a "todo" in the room then a "unread messages" indicator or even a counter. This fits also better with the very common behaviour of user marking rooms as "unread" to remind them self to answer later or to revisit the room at a better point in time.

We need to meet the fine line of making users aware and annoying them so it should be fairly easy to "remove" the unread indicator for a room. Todays behaviour of keeping a room un-read just because there are messages unread in a Thread is a god example of annoying behaviour - and it is inconsistent. While a room is marked as read even though I may not have been reading through all messages (especially in very big room with a high frequency of messaging) I am forced to visit every single thread or mark the room as un-read manually.

Scope

These should be a list of technical tasks which take ½-1 day to complete

Tasklist

Preview Give feedback

1. Implementation
2. QA signoff on completion
3. Design signoff on completion
4. Product signoff on completion
5. Self-sent msgs mark rooms as unread vector-im/element-x-ios#639
   A-Room-List O-Occasional S-Major T-Defect Z-Schedule +5
   
6. A room that has predominantly images doesn't clear unread marker #1977
   A-Read-Marker App: ElementX Android App: ElementX iOS O-Occasional S-Major T-Defect X-Needs-Rust Z-Schedule +8

Stretch goals

None at this time

Out of scope

[callumu]

Bug from a room that has predominantly images

RPReplay_Final1690985071.MP4