[Bug] Create workflow + invite issues: Signup asked twice

[spolu]

See https://groups.google.com/a/dust.tt/g/product-archive/c/O89zxFs9rN0

When signing-up and verifying email when coming back the page still asks to sign-up

Important because this is the flow we use for our enterprise users

[philipperolet]

Investigation going on in this sister issue, the issues seem to have the same root cause

[philipperolet]

See sister issue investigation for context

It's confirmed that when going through a regular invite, a user that did not have a pre-existing auth0 entry -- which will always happen if choosing to create a password -- will get to the invitation screen twice:

1. when clicking on the email invitation link: at that time, goes direct to invitation screen, no user is created on dust nor on auth0
2. after successfully logging in via auth0: at that time, auth0 redirects to dust.tt home, which sees a user with an invitation token and and redirects to invitation screen (at that time also creating the user if not existing already)

This is at the root of confusion

[philipperolet]

Sitrep for this issue
What happens is:
Clic on invite link -> Invitation screen-> password auth -> verification link -> /api/login?inviteToken -> user creation -> redirection to invitation screen again

When a user was just created and has an invitation link, we redirect him to the invitation screen.

Next step:Find a solution to detect when the user already comes from a signup screen (cookie, in-db value, get param transmission...)

Although this PR might lead to believe it's actually not trivial #6034