New node configuration format

[joelwanner]

To generate the configuration dynamically, the nodes.json file needs some additional information. Here's a proposal for the fields needed for each node entry:

• public-ip: Public IP for remote (SSH) access.
• scion-ia: SCION ISD-AS identifier.
• int-prefix: IP prefix used for communication within the SBAS. No two nodes may have overlapping internal prefixes.
• int-sig-ip: IP address for local SIG (from the internal prefix).
• ext-prefix: IP prefix that belongs to this node, announced to customers.
• ext-vpn-ip: IP address that customers use to set up VPN tunnels into the SBAS node. Also used by VPN servers to interconnect.
• peering-mux: Name of the PEERING mux to connect to.
• vpn-key: Public key for WireGuard server.

[liangw89]

The node should be configured with a public key as WireGuard uses public keys as IDs

[joelwanner]

Good point, thanks! I've added it to the list.