Invite user UX is confusing

[lampholder]

Split out from element-hq/element-web#6599

Independent of the search behaviour is the search UX. I think we've got two main problems:

• the UX doesn't explain to the user the caveats around their search
• the UX does not distinguish between:
  • real users with default avatars and no display name
  • valid mxids that the homeserver knows does not represent a real user
  • valid mxids that the homeserver isn't allowed to confirm whether or not is a real user
  • valid mxids that the homeserver cannot tell whether is real or not due to federation
  • valid mxids that the homeserver cannot tell whether is real or not due to bridging
• @AmandineLP suggests we could prioritise users from your homeserver in the invite UX (Users from one's own server should be prioritised in the search results element-web#6478)

[lampholder]

I think we could make a significant improvements to the UX if:

• any valid mxid that the homeserver can't or won't confirm is a real account (for whatever reason) should appear in grey with a grey default avatar (maybe with a question mark instead of the initial avatar)
• the search dialogue could report the status of search_all_users and explain the consequences

Even better if valid mxids that aren't real users could appear in red and block the invite's sending (but I reckon that's going to be a lot more fiddly to impl).

[t3chguy]

Moved to meta as this should be consistent between the apps, also some issues like

the UX doesn't explain to the user the caveats around their search

Are implementation specific so the client can't know what the specific caveats are as it depends on the server they're connecting to