Add instagram background implementation and generalize application for other identity providers

spec/acceptance_steps/global_user_steps.rb

@@ -29,7 +29,7 @@ step "the user should be redirected to the archived list path" do
 end
 
 step 'there is another user' do
-  @other_user ||= create :user
+  @other_user ||= create :user, :other_auth
 end
 
 step "the other user clicks the join table button" do

spec/acceptance_steps/users/join_request_steps.rb

@@ -4,7 +4,7 @@ step "the original user should see a join request message" do
   request_title = page.evaluate_script(%|t('join_request.existing_user.title')|)
   request_title.should be_present
   page.should have_content request_title
-  page.should have_content @other_user.email
+  page.should have_content "UOther" # spec/factories/user
 end
 
 step "the original user should not see the join request anymore" do