- Use `user` everywhere, instead of sometimes `loggedUser`
- Delay the instantiation of some variables: no need to perform SQL queries for
nothing.
- Remove a SQL query getting the whole user struct when only user.ID is used.
Each batch of feeds sent to the worker pool is now guaranteed to contain unique feed URLs.
When `POLLING_LIMIT_PER_HOST` is set, an additional limit is applied to the number of concurrent requests per hostname, helping to prevent overloading a single server.
Note: Additional requests may still be made during feed refresh. For example, to fetch feed icons or when the web scraper is enabled for a particular feed.
