* chore: convert workspace agent stats from json to table
* chore: convert agent stats to use a table
Backwards compatibility becomes hard when all agent stats are in a JSON blob.
We also want to query this table for new agents that are failing health checks
so we can display it in the UI.
* Fix migration using default values
feat: Add initial AuthzQuerier implementation
- Adds package database/dbauthz that adds a database.Store implementation where each method goes through AuthZ checks
- Implements all database.Store methods on AuthzQuerier
- Updates and fixes unit tests where required
- Updates coderd initialization to use AuthzQuerier if codersdk.ExperimentAuthzQuerier is enabled
