Utilize SolidusAuthDevise redirect helpers

With the deprecation of #redirect_back_or_default in solidus 4.0,
we can utilize the SolidusAuthDevise helper stored_location_for
to provide the same functionality.

Author: cpfergus1

app/controllers/spree/omniauth_callbacks_controller.rb

@@ -21,7 +21,7 @@ def provides_callback_for(*providers)
   def omniauth_callback
     if request.env['omniauth.error'].present?
       flash[:error] = I18n.t('devise.omniauth_callbacks.failure', kind: auth_hash['provider'], reason: I18n.t('spree.user_was_not_valid'))
-      redirect_back_or_default(root_url)
+      redirect_to stored_spree_user_location_or(root_url)
       return
     end
 
@@ -34,7 +34,7 @@ def omniauth_callback
       spree_current_user.apply_omniauth(auth_hash)
       spree_current_user.save!
       flash[:notice] = I18n.t('devise.sessions.signed_in')
-      redirect_back_or_default(account_url)
+      redirect_to stored_spree_user_location_or(account_url)
     else
       user = Spree.user_class.find_by(email: auth_hash['info']['email']) || Spree.user_class.new
       user.apply_omniauth(auth_hash)

spec/controllers/spree/omniauth_callbacks_controller_spec.rb

@@ -9,15 +9,15 @@
     Rails.application.routes.default_url_options[:host] = 'test.host'
     request.env['omniauth.auth'] = omni_params
     allow(controller).to receive(:sign_in_and_redirect)
-    allow(controller).to receive(:redirect_back_or_default)
+    allow(controller).to receive(:redirect_to)
     allow(Spree::User).to receive(:anonymous!).with(user)
   end
 
   shared_examples_for 'denied_permissions' do
     before { request.env['omniauth.error'] = 'FAIL' }
 
     it 'redirects properly' do
-      expect(controller).to receive(:redirect_back_or_default)
+      expect(controller).to receive(:redirect_to)
       controller.github
     end
 
@@ -95,7 +95,7 @@
         end
 
         it 'redirects properly' do
-          expect(controller).to receive(:redirect_back_or_default)
+          expect(controller).to receive(:redirect_to)
           controller.github
         end