Fix purge_cache by specifying a path instead of a `path` parameter

[knu]

Zone#purge_cache is broken in that it posts to the wrong endpoint zones/:id?path=purge_cache instead of zones/:id/purge_cache. Representation#with does not take a path argument, which could be the root of the problem.

[ioquatix]

Thanks. I will review it when I have time.

[knu]

I've added a call of post and the method should now perform properly. 😅

[ioquatix]

I'm pulling the branch locally so CI can run.

[ioquatix]

Is there any kind of test?

[ioquatix]

Thanks, this is merged.