qt: Add API for ContentRating descriptions

[aleixpol]

No description provided.

[ximion]

I think this patch is okay, but wouldn't you also need a wrapper for as_content_rating_get_rating_ids to make efficient use of this API?

[aleixpol]

Yep, added

[ximion]

Looks good! I do wonder now whether there will be a time where you'll also want a attributeDescription(id, value) API that isn't dependent on having a ContentRating object, like the C API has. But we could add something like that later, in that case... (or of course follow the C API and have these functions separate, but tbh I don't mind that description() convenience function :)

[aleixpol]

I am not sure in which case we'd need a description without an ContentRatings object.

FWIW, this MR uses this new API https://invent.kde.org/plasma/discover/-/merge_requests/357

[ximion]

I am not sure in which case we'd need a description without an ContentRatings object.

Mostly useful if you want to contruct some kind of overview page :-)