Pass ?qrcode=true as query string

Can use:

  -  /api/items?serial_number=123456
  -  /api/items?location_id=1

- add more tests
- patching an item update children location and status
- setting the parent on an item updates the location and status with the
  parent ones

Most items won't have a name.
hostname could be added in a separate table if required.