fix: wrong json property name for difficulty rating

[matte-ek]

Fixes some minor stuff I caught while trying out the library today.

• Rename DifficultyRating to StarRating as per the osu! documentation
• Add description attributes to RankedStatus enum since otherwise the GetBeatmapAsync request would cause an exception

I was going to add the ability to pass mods onto the GetDifficultyAttributesAsync endpoint, but it seems like the API expects the data in the body of the request as JSON, and I wasn't sure how you would like to deal with cases like these, my changes FWIW.

Nice work on the library so far though, nice and easy to work with, and code is very nice.

[minisbett]

Thanks!

Yeah those two are oversights. Although the RankedStatus has already been fixed, the star rating field name was definitely an oversight. As for passing mods to GetDifficultyAttributesAsync, I can add that, sure.

[matte-ek]

Oh I see, didn't see that commit. Dropped the commit from my branch in case you want to merge this one.

[minisbett]

If you'd be interested in contributing by adding mod-support for the difficulty attributes:

The way I'd imagine an implementation would simply having 3 different overloads for specifying either a string (eg. HDDT), an array, or the bitwise integer flag. It seems like I also didn't implement the ruleset parameter, which could be implemented there. (ruleset_id can be ignored)

As for the fact it is a post request, I currently have my main request handler GetFromJsonAsync, which I manually pass a HttpMethod.Post to. A dirty hack, I know. Maybe it could be split up into a GetAsync and PostAsync, which both have their own specific code but call a private method inside OsuApiClient (eg. SendAsync) which then handles all the other request-related code. The PostAsync method could then allow for specifying the body, which is required to pass mods & co.

Edit: I checked your changes you linked, and I think they're pretty good. Feel free to PR them so we can work from there!