Logout endpoint

[JMante1]

This issue is related to flapjack API?
Yes

Describe the bug
I can't find an api endpoint to logout. I can find an access token, and a refresh endpoint but not a logout endpoint

To Reproduce
No error as it is missing

Expected behavior
I expect something like the refresh endpoint where I can send the access token and it will return 200 to confirm I have logged out.

[JMante1]

@timrudge