bug(billing): Don't allow email to be changed via Stripe Customer Portal.

[elliotcourant]

Right now when a user navigates to manage their billing we bring them to the customer portal inside of stripe. This portal allows them to update their email, which might cause their email address for billing to be different from their email address for monetr itself; making it harder to cross reference the two quickly.

Instead allow the email to be changed in monetr and then once the email is verified update it inside of Stripe.

However things that monetr does not need to keep track of such as phone number (if for whatever reason they provide it to Stripe) or address should be able to be updated via the portal.

https://docs.stripe.com/api/customer_portal/configurations

https://docs.stripe.com/customer-management/configure-portal