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At step 4 in the main success scenario, should we skip the email validation process that precedes registering an account?
+ Easier to use for the user.
- Forces the user to register Synapse account with the email address the invitation was sent to.

Leaning towards yes, we should skip it.

Related to the above, should the invitation email have one link to a sign in/registration page; or two links, one to a sign in page and one to a registration page.

Tentatively a single link is preferred.

Should we allow batch inviting? Currently only one user can be invited at a time.

Not necessary.

Should we display pending invitations in Alice's team page and allow her to cancel them? This would remove the need for the alternative scenario on step 5.

Yes, it's a good idea as it enables alternative scenario step 3.

What happens if the invitee is already signed in to Synapse when they click the invitation link(s)?

Addressed by alternative scenario step 4a.

Should we allow existing users to be searched by their email address?

No, we shouldn't allow reverse searches because user email addresses aren't public.

Mockups

In progress

API

In progress