Preview thread invite block data before join

[sanderpick]

Is your feature request related to a problem? Please describe. Also from convo w/ @advatar, when you receive an invite, there's no way to know:

• initiator
• thread type
• sharing type
• schema
• member list
• etc

You want to have some idea about what this thing is. Who's in there? What's it for?

Describe the solution you'd like All the data is there in the invite block, we just need to show it as a "preview" before they actually join.

Additionally, we could add some thread metrics to the invite block:

• member count
• file / message count
• last updated
• top 5 most active members?
• others?

Additional context We currently show the "inviter" and "name" in the invite URL for an external invite. This would no longer be needed if you could see the whole block's data as inviter is in there.