Feature that allows superusers to accept invitations on behalf of the users that were invited

[KarthikRaja1388]

Summary

Sometimes contractors work on Matomo implementations who are at the office for only one day per week. When setting up these users the invitations sometimes expire before the users see them, and then I have to set up those users all over again, because apparently the user is also removed once the invitation expires (although there is filter for expired invitations in the "Manage Users" interface).

[sgiehl]

There is a config option called default_invite_user_token_expiry_days, which allows to extend the expiry time. For such a case I think it makes more sense to extend that.