enabling json post requests to invalidate_sessions

[tejon-melero]

What happens right now:
since the function invalidate_sessions looks in the POST body of the request for the client id, at the moment this endpoint only works when clients post to this endpoint with form-data --> content type application/x-www-form-urlencoded or multipart/form-data

What should happen:
the invalidate_sessions endpoint should also accept content-type 'application/json'.

Django Rest Framework's data field takes any type of content type in post requests and makes it accessible.

[fthuin]

Great ! It works for me, wasn't able to use the view with application/json 👍

[fthuin]

@PhilipGarnero Any update on this? I had to create my own view with a copy/paste of the code of this pull request to handle it, which I don't like because I want to keep compatibility with newer versions.