Dynamic stripe portals per organization

[elboletaire]

Our current stripe integration links the account paying the subscription with stripe, making this account the only one able to manage the subscription.

Stripe has a way to create portal sessions, allowing us to not just remove the screen in the middle asking for a login, but also allow any organization admin to manage the organization subscription.

Integrate customer portal: https://docs.stripe.com/customer-management/integrate-customer-portal#redirect
Create customer portal sessions via the API: https://docs.stripe.com/api/customer_portal/sessions/create

Since we've been creating stripe clients using the e-mail, we'll have to take into consideration how to migrate or treat new accounts, without losing the subscriptions which are already working.

Since customers require an e-mail, and the new identifier may be the organization public address, this should not be a problem. We should be able to simply add the address as a customer metadata, and maintain the email of the person who payed that subscription for the first time both for backwards compatibility and for data coherence.

The process should be quite straightforward:

• When paying for the first time an organization subscription, create the stripe customer using that user email for the customer account, and the organization address as metadata.
• Create a backend endpoint to start portal sessions based on the organization address. Note this endpoint should only be accessible by admins and managers.