Do you think it is fair to pay $10 to solve this problem?

Sometimes it looks complicated, but if you already worked with something like that, it is an easy task, maybe just some lines.

People answers questions in StackOverflow for free, so sometimes $10 is a good reward. I don't know the answer to this bounty, so I will not use my time to learn omniauth and answer the question, it is not worth $10.

Well, you're free to decide, aren't you?