Added Omniauth Google Oauth2

[mghaught]

Currently a WIP but the basic flow works.

[barrettclark]

I think this looks good. There may be some rough edges to smooth out for cases where you do not use all 3 OAuth providers. Most of those look like you could add some simple checks like you did in the application helper, probably with the exception of the user model.

If those checks end up being useful in other places maybe you could do something in an initializer and add them to the application's config. Maybe something like this:

# config/initializers/oauth_providers.rbRails.application.config.oauth_providers=ActiveSupport::OrderedOptions.newRails.application.config.oauth_providers.github=ENV['GITHUB_KEY'].present?Rails.application.config.oauth_providers.google=ENV['GOOGLE_OAUTH_CLIENT_ID'].present?Rails.application.config.oauth_providers.twitter=ENV['TWITTER_KEY'].present?

We actually have a gem at TCS that does something similar to this. We load a YAML file and the gem then knows how to get data from the environment, consul, or vault.