Invoice email burndown

[ackernaut]

Here we’re tracking issues for a complete UX for automatic invoice emails:

• Designed managing invoice recipients #6570
• Generating an invoice PDF #6573
• Designed updates to invoice and invoice section #6575
• Implemented invoice PDF #6576
• Invoice email copy and design #6571
• Implemented invoice email #6577

[mattkrick]

I think we should avoid printing PDFs.
Instead, we should email the billing leaders telling them that an invoice in ready & they can login to view it.
This is cheaper, more secure (no billing data sitting in your inbox forever), and if they want to print the PDF from our webview, they can.

When stripe tells us there's a new invoice, we should generate it & fire off an email to the customer letting them know. That should be ~13 hours of implementation work.