[RFC] Internationalization system rework

[keats]

@southerntofu

This way no need to worry if someone is translating author to “auteur”, “auteure”, or “auteurice” (gender variance). This approach would still enable to have language-specific taxonomies, by not specifying an id. The same translation strategy could be applied to taxonomy terms.

I kind of like using the given name from the taxonomies so we don’t mix languages. We error if the taxonomy is not found in config.toml anyway so someone putting auteure when the definition has auteurice will fail.