More userfriendly error message for invitations that are not available anymore

[baszoetekouw]

Currently, users get a 404 age with a custom error:

The focus is currently on the 404 error instead of on the message. We should improve these pages.
Distinguish two cases:

• Invitation is expired/deleted/no longer available: use the existing page but with a nicer message/image (no 404)
• In addition, the user is already a member of the collaboration: maybe just show the CO page with a modal/bar/message "you are already a member of this collaboration". (Use case: users has already probably accepted the invitation.)

Second user story split off to

• As a user accepting an expired/invalid invite to a collaboration I'm already a member of, I want to get told I'm already a member #1578

[FlorisFokkinga]

How about this design?

[oharsta]

3e6a279

[mrvanes]

The "accepted invitation" flow also shows the expired/deleted/no longer available page. Is that correct?

[FlorisFokkinga]

@oharsta Could you also add a message for when the user is already a member of the collaboration, per the second bullet? Is this information already available?

[oharsta]

@FlorisFokkinga This is already covered in the current version.

[mrvanes]

Works as expected for new invitation links, done