Abstract away each sites device configs into a central set of templates

[michael-robbins]

Currently each site has its own device configs that are very similar for their function (eg a firewall across the hubs will be roughly the same + site specific extras)

So we should try abstract away each sites fw-0 device into a single template and render them out correctly.

This is a bit of a 'how long is a piece of string' type issue, so just start with fw-0 for hubs first, then we can go from there in future issues if this is a success.

A great example of the abstraction possibilities is the VLAN network configuration, this is all stored in each sites networks.yaml and also hardcoded in the device config, if we could use the tera templates to interpret the networks.yaml config and produce the VLAN configuration in the device config that would be awesome!