added remove_release to collection folder

[AnssiAhola]

Implements this API as requested by @raratiru in #86
Not the most elegant solution but it works 🤷

@JOJ0 @alifhughes
If you could check this and test it, I'd appreciate it 🙂

Not sure if delete_instance is good name for the method, maybe delete_release to be consistent? Although it needs CollectionItemInstance as the instance id is required in the url.
Maybe it should be remove_release or remove_instance like @raratiru suggested?

Any suggestions are appreciated! 😅

Usage:

user = d.user("example")
folder = user.collection_folders[1]
releases = folder.releases
# Delete the first instance in releases
folder.remove_release(releases[0])

[JOJ0]

I vote for add_release vs remove_release. Thanks @AnssiAhola, hope I will manage to test tomorrow or Thursday morning.

[JOJ0]

What I dont understand from reading the discogs api docs you posted @AnssiAhola: It will remove the release instance from a folder, ok, but when removing from the uncategorized folder, I think the one with folder id 0, does it mean it will be removed from the collection entirely? That right? It would make sense but it's not entirely clear to me from reading the doc.

Update: Ok that was silly, we give the instance id in the url_

[JOJ0]

Let's merge this so @raratiru can use it and do docs later on.

[raratiru]

Thank you, this is a great addition!

[AnssiAhola]

@raratiru This will be merged and (hopefully) released tomorrow if everything goes to plan 🤞