API Client authentication not working

[grahampugh]

I had made an assumption that the output of /api/oauth/token would be the same as that of /api/v1/auth/token, but it is not.

In /api/v1/auth/token, the token key is token and the expires token is expires.
In /api/oauth/token, the token key is access_token and the expires token is expires_in.

Furthermore, the time outputted from the expires key differs; a timestamp vs. the number of seconds until expiry.

[grahampugh]

This is partially fixed but note that renewal of API Client tokens is not supported. I'll leave this open for now to check if that's an issue.