[Feature Request]: Add ability to create a ZT "moon"

[FallenChromium]

🚀 Feature Summary

Adding an option to host a moon would allow to serve a custom root for the network without disconnecting it from the ZT default roots

📝 Detailed Description

This feature is for adding an additional L1 backbone to a zerotier network without leaving to a separate zerotier planet. It is useful for cases when some (but not all) network endpoints are isolated from a ZT root (think censorship or corporate firewalls), but other devices might benefit from connectivity to ZT central roots, such as mobile phones (connecting to a custom planet is problematic on the mobile clients). Moons (see docs) can give a great boost in connectivity throughput in firewalled environments or can be a privacy-enhancing feature without breaking the comfort of discovering a network through the default roots

🎯 Use Case

Not that much to add, I'd just like to have a custom root if my home lab will have problems with internet connectivity (I have a separate channel to a controller that is neither internet or a local network, because no multicast is allowed through this path, local peer discovery won't work). Moon is an ideal solution to this problem.

💡 Willing to Contribute

Yes, I could help with testing