Add sorting to find jobs API

The find jobs API, `/api/jobs?filter=&offset=&limit=`, should also support server-side sorting. 

Requirements:

- The API supports sorting on the same columns that can be filtered, excluding the `tags` filter, i.e.
  - `company (name)`
  - `location`
  - `country (name)`
  - `seniority`
  - `salary`
  - `remote`