OAuth 2.0 in emacs – Part 3

I’m still stuck with WordPress and OAuth 2.0. I sent a support email to them but they have not followed up yet. I did find the problem described on Stack Overflow with no solution yet either.
I thought I might try and get OAuth 2.0 working with a different service.
Twitter does not appear to officially support OAuth 2.0 yet. Twittering mode in emacs authenticates with OAuth 1 and appears to have its own code for doing so.
My next thought was to see if I could find a test OAuth 2.0 server to do my own testing on. I found there is a discussion and links to one on Stack Overflow, but its OAuth 1.
Google! of course, google supports OAuth 2.0. My next steps will be to see if I can authenticate against that from emacs.
A quick search of ELPA revealed the google-contacts package and lo and behold! it was written by Julian Danjou who wrote the OAuth 2 library I am planning to use. It looks like a really good example to follow too.
Then I had the idea that maybe if I try the authentication against a blog hosts on wordpress.com rather than my self hosted WordPress site. And sure enough, that works. So I’m back in business. More in part 4.