[Feature] Implement data usage information endpoint (`/system/df`)

[ChiaraBm]

Hey,

Thanks a lot for maintaining this fork—really appreciate it since the original repo seems unmaintained ❤️

I noticed the library is currently missing the /system/df endpoint.
Would it be possible to add support for it?

Thank you very much in advance

[HofmeisterAn]

Thanks for creating the issue. Of course, we can add the API to the library. Are you interested in contributing?

[ChiaraBm]

Yes i am interested. I'll have a look at it during the next week :)

[ChiaraBm]

So i checked out the generation of the models and noticed that the system df endpoint is currently not released in the docker client. it is contained in api/v1.52.0-beta.0 which is not yet released (even tho docker supports the endpoint since months). I would wait until they put out a new release and then start working on implementing this endpoint :)