This PR refactors the configuration parser, replacing the old parser implementation with a new, more structured approach that includes validation and improved organization.
Key changes:
- Complete rewrite of the configuration parser using a map-based structure with built-in validation
- Addition of comprehensive validator functions for configuration values
- Renamed numerous configuration getter methods for better consistency
- 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.
