The * GET /wireguard/config/<instance-id>* resource returns the
WireGuard client configuration assigned to the specified instance ID.
The resource contents are stored in the Kubernetes Secret, in a data
field named `wireguard-config`. The contents of this field are returned
directly as a string, without any transformation. Thus, the value must
be a complete, valid WireGuard configuration document. Instances will
fetch and save this configuration when they first launch, to configure
their access to the VPN.
Dustin