Previously accepted invites should redirect to the GitLab product
Currently, if a user selects "accept" on an invite they've previously accepted we direct them to a GitLab 404 page as the invite token has been deleted since the invite has already been accepted.
Why this matters from a user perspective
As a net user of GitLab, I may accept the invite login then a few hours/days later may think to "re-login to that platform I was recently invited to" and instinctively open and select "accept" in the invite email to get back to GitLab.
If a user selects "accept" in a previously accepted email we should redirect them to the GitLab product. We should treat this like anyone link that sends someone into the product whereby we try and give them access to the product directly but if they're not actively logged in then the user lands on sign_in.