Move to using tetcd

[NHAS]

Use a typesafe etcd code generator to enable automatic db layout.

https://github.com/NHAS/wag/tree/v10.0.0-typed-etcd-gitops

This means that when code changes are made all decisions are explicit and it becomes easier to programmatically interact with the DB.

This effectively enables #243 to be completed

[NHAS]

Work:

• Refactor the majority of the functionality in db to use tetcd
• Define structures to represent db layout
  • Move db structs to their own package/s
• Add migrations from 9.1.7 (by hand for one major version)
• Define way to json diff that matches tetcd path determination (might be done in tetcd)
  • Refactor initial load logic based on this
  • Apply json diffs with rollback on error
• Generate a bunch of unit tests for db for fun