merge develop into production
- Update PaymentServer (!276 (merged))
- Update nixpkgs for Linux 5.10.103 (!277 (merged))
- Factoring improvements (VPN client, monitoring exporters) (!217 (merged))
- Grafana: Payment dashboard: Revert "Redemption" back to old-style Graph panel (!270 (merged))
- nixpkgs update 2022-02-28 (!275 (merged))