Read the VPN server IP address from the monitoring node config
Merged
requested to merge 207.reuse-vpn-server-ip-configuration into 207.payment-server-exception-reporting-update
morph offers an auto-passed nodes parameter from which we can read all of
the nodes in the morph "network". We can dig around in this to find the
monitoring node and then read its configured IP address.
It may be worth noting that this address appears in at least two places in the
configuration. It appears in our "input" configuration which grid.nix
defines. This change reads it from there. We also have a NixOS module
nixos/modules/monitoring/vpn/server.nix which reads this "input" and uses it
to configure networking.wireguard.interfaces.monitoringvpn. This is fed
onwards to to generate actual system configuration.
It seems better to use the former than the latter because we have more direct control over it and if we consider the whole configuration system a function then it is more like an argument we are supplying rather than an obscure implementation detail.