HIGH: "Refactor "Workspace welcome message" to be "Workspace description" (1/2, internal)

[quinthar]

Problem: Right now when you go to invite someone to a workspace, you can provide a custom invite message. But you'd never guess that the message:

• Is saved for the next invite
• Is also shared with new employees in the Workspace Chat

So it's not really an "invite message", it's more of a description.

Solution: Mirror the design of the room description and refactor the server and client to call this a "workspace description", which is more intuitively accurate. This consists of:

1. add an updateWorkspaceDescription API command that updates a description attribute of the workspace
2. return this description along with the workspace object
3. update the client to use this description everywhere the "welcome message" currently is.

Note: we will leave the invite message as-is on OldDot.