If you've configured your Doorkeeper with the default settings it will not allow you to put
localhost:3000 as the redirect callback because it requires an SSL protected redirect. For staging apps you may want to set
force_ssl_in_redirect_uri false in your Doorkeeper initializer.
However, you may want to test your local app against a live OAuth provider with a callback URL that imitates your client application's protocol, i.e. https://app_name.dev/
Configuring Pow with NGINX and SSL on OSX
Follow these instructions, they're very thorough: http://matthewhutchinson.net/2013/6/20/configuring-pow-with-nginx-and-ssl-on-osx. This will tell you all you need to know to get https://app_name.dev.
jRuby error: IOError: Socket is not connected
Getting the error above? Hack pow to make it work until jRuby fixes this issue: https://gist.github.com/tonyhuynh/bf157f12813f26736513
Read more about the issue: https://github.com/basecamp/pow/issues/14