[C-2046] Workspace invitation link

[nunoeufrasio]

| “It would be cool if admins could create a link for self-signup of new members. This could then be placed in internal gihtub repos, wikis “ |

Include in "Invite users" dialog a self-signup invitation link that admins can copy to clipboard. As a security measure, only users that match the workspace owner (1st user) email domain can sign up successfully via this link.

This design already includes iterations on behalf of UX Debt project (e.g. invite multiple users at the same time). Not all design updates must be followed on behalf of this issue.

_{From SyncLinear.com | C-2046}