Firebase uid, or the email address on the account. The uid is what everything below acts on — an address is only a way of finding one.
Change the licence
Use this for what Stripe cannot express: a partner studio, a refund that left the
subscription in the wrong state, an account suspended during an investigation and
restored after it. A hand-granted licence is marked as one, so nothing downstream
mistakes it for a payment.
For a stolen laptop, or a studio that has been reimaged.
Mail
The last two hundred automated emails, the ones that did not go first.
It cannot take a payment, refund one, or change what anybody is charged — that is
Stripe's, and it stays there. It cannot read a customer's password or their files.
And it cannot make a change without recording it: there is no route through this
page that leaves no explanation.