Plan change via backend is not redirected to the payment page

[ptruessel]

If a customer decides in favour of a paid plan and wants to carry out an upgrade via the backend, they are redirected to the payment methods if they have not yet entered a payment method. Once they have entered a payment method, they are redirected to the payment methods again without the booking having taken place. They must now go back to the plans and select the plan. This should be adjusted.

Idea: add the redirect (bookin link) to the button and book the plan immediately, even if the first payment method is entered.