This is a huge configuration refactoring.
The configuration system now uses Pydantic settings, with better validation, better
support for environment variables and other goodies.
The main config files now use TOML instead of INI, this allow for better handling of
complex types, notably dict.
Plugins, components and frontends can declare their config settings in a class which will
be imported dynamically.
- Generated password must now be named and are stored, so they are re-used on following
restarts. Password size can now be specified.
- New `not` filter for `!libervia_param` to inverse a boolean value.
- Former `front_url` field has been renamed to `web_url_path` as it is the URL path used
for web frontend. All Web frontend related field are prefixed with `web_`.
- `front_url` is now used to specify a whole front URL (notably useful if an app uses its
own domain). A list can be used to retrieve a key, like for `url_prefix`, and `https`
scheme is added if no scheme is specified.
- An abstract class is now used for App Managers.
- Last application start time is stored in persistent data.
