Update path_prefix default to match the old default

[swrobel]

The old route was /users/auth/:provider and this has changed the default to /user/auth/:provider
I believe the default should not break existing apps that were relying on that route

This should be committed to 2-0-stable && 1-3-stable as well

[radar]

Added to master, 1-3-stable and 2-0-stable. Sorry for the delay, I was on vacation last week and I'm still catching up with emails.

[swrobel]

No worries, glad to have you back!

[radar]

This seems to now be causing #130. I think that if we changed the option to spree_user by default it might fix that issue.

[j-mcnally]

If we allow the user to change this we need to document that the omniauth failure block should be hardcoded to the spree_user mapping.

OmniAuth.config.on_failure = Proc.new do |env|
  env['devise.mapping'] = Devise.mappings[:spree_user]
  controller_name  = ActiveSupport::Inflector.camelize(env['devise.mapping'].controllers[:omniauth_callbacks])
  controller_klass = ActiveSupport::Inflector.constantize("#{controller_name}Controller")
  controller_klass.action(:failure).call(env)
end

[troelskn]

I spent quite some time on getting this to work, so I'll just leave this here for the next poor soul who arrives here. You need to load devise before setting up this custom failure block - otherwise it'll just get overridden by devise's block. Simple put require 'devise/omniauth' on a line before.