[Pay-as-you-go] Enable email invoices for Stripe subscribers

[jldec]

Pay-as-you-go users should be able to request invoices via email.
Currently their only option appears to be to to go to the Stripe portal via the link in their Billing settings page.

Ideally it should be a flag in the portal to turn on/off emails, and they should be on by default.

[gtsiolis]

Alternatively, or additionally, we could add a new page for all the invoices issued so that users can self-serve and download their invoices without sending a request that. needs to be performed by our team. 💡

[jldec]

Current Stripe users do receive their invoice by email if it has an amount > 0.
Closing