Tidy up ORM schema for v2

[splushii]

As we need to bump the ORM schema for v2 it's a great opportunity to go through the schema and make changes where needed. For example streamline the key names and fix typos.

[splushii]

For example, I would like to

• Rename actions.backend.servers to actions.backend.origins, to use the same terminology as the singular equivalent actions.backend.origin
• Rename matches.-paths to matches.-path, to make all matching functions use singular form.