New "Payer" role for Heroku Online Teams

### Required Terms

- [X] I agree to follow this project's [Code of Conduct](https://github.com/heroku/roadmap/blob/main/CODE_OF_CONDUCT.md)
- [X] I have read and accept the [Salesforce Program Agreement](https://www.salesforce.com/company/program-agreement/)

### What service(s) is this request for?

Heroku Teams

### Tell us about what you're trying to solve. What challenges are you facing?

What is missing from the Heroku Teams is a "Customer" role that has access to the credit card information and invoices but cannot remove other team members or transfer the application. Customers would like to (and should) be independent from the developer w.r.t the billing of an app, so if something happens to the developer they can still use the app.

Currently, the only way to do this is by creating a Team and give Admin privileges to the customer. However, as an Admin the customer may remove other team members (i.e., the developer) and hijack or even transfer the application to other Heroku accounts.

This would be a great feature to implement and one that is not offered by anyone else....