Profile interop: Send avatar and thumbnail as attachments

[vintprox]

#70 mentions:

3D avatar / thumbnail should be saved in m.world.profile room state event

So we can assume it's planned to be state events for now as a primary data point in profile type rooms. My only issue with this is interoperability:

• one needs to do extra steps to download their backed up model/sprite, as well as to see related thumbnail, from any other client;
• profile room will just look empty or have events of which only Third Room client can make sense.

I propose such binary data to be sent as attachment instead of room state event.

[vintprox]

If the problem is how to pack everything together under one avatar, there is such thing as relations. I presume we can take attachment and put into it a relation to original event that describes single avatar (which in return can remain room state event, or even better - a message with HTML/text description that other clients can simply show above those attachments).

[ajbura]

If we send m.world.profile as message and attachments in relates to original message we will not have a direct way to look profile either we have to backfill timeline until we find relevant event or we need to remember the event id to access it via /context api.