Change how hostname/devices work

[ErikBjare]

A few things we should consider changing:

• Every device/installation should have a unique ID (a UUID) that does not change if the hostname is changed.
  • Completed in Added device_id and exposed it through /api/0/info aw-server#61 and Added device_id and exposed it through /api/0/info aw-server-rust#69
• If a bucket is created with a special hostname/UUID "local" or similar then it should default to the hostname/UUID of the running instance.
  • Or it should be the responsibility of the watcher to retrieve the UUID from /api/0/info and use it during bucket creation. Although defaulting to the local value seems like better API ergonomics (and would maybe make migration easier).
  • As an example, it is required for the web watcher to work properly with sync (see Multiple web watcher buckets per instance broken due to hostname unknown #307)
• Additionally, we might want to move the hostname (later UUID) bucket attribute into the data field of buckets. This would impose specific semantics on the data field of buckets (which we currently lack) so might need further discussion (i.e. which data attributes are reserved for internal use in aw-server?)

Originally discussed here: ActivityWatch/aw-server-rust#61 (comment)

[johan-bjareholt]

Another thing, we might want to make buckets user-specific on platforms which have multi-user support.
See this forum post
https://forum.activitywatch.net/t/add-windows-username-to-bucket/374/2