Postgres backups stored in same region as database

### 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 Postgres

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

All [PGBackup](https://devcenter.heroku.com/articles/heroku-postgresql#data-residency) snapshots are stored in the US, regardless of where the database is hosted. As far as I know, this applies to the EU common runtime and private spaces.

One selling point for a private space is meeting data residency requirements. Keeping backups in the US does not meet this requirement. Maintaining our own backup infrastructure and disaster recovery procedures incurs extra costs and reduces the product's value.

Apologies if this is a duplicate; I was surprised that I couldn't find this proposal already.