Move omniauth form partial to a component

This way we simplify the view a little bit and replace some slow system
tests with faster component tests.

spec/components/devise/omniauth_form_component_spec.rb

@@ -0,0 +1,56 @@
+require "rails_helper"
+
+describe Devise::OmniauthFormComponent do
+  describe "#oauth_logins" do
+    let(:component) { Devise::OmniauthFormComponent.new("sign_up") }
+
+    before do
+      Setting["feature.facebook_login"] = false
+      Setting["feature.twitter_login"] = false
+      Setting["feature.google_login"] = false
+      Setting["feature.wordpress_login"] = false
+    end
+
+    it "is not rendered when all authentications are disabled" do
+      render_inline component
+
+      expect(page).not_to be_rendered
+    end
+
+    it "renders the twitter link when the feature is enabled" do
+      Setting["feature.twitter_login"] = true
+
+      render_inline component
+
+      expect(page).to have_link "Twitter"
+      expect(page).to have_link count: 1
+    end
+
+    it "renders the facebook link when the feature is enabled" do
+      Setting["feature.facebook_login"] = true
+
+      render_inline component
+
+      expect(page).to have_link "Facebook"
+      expect(page).to have_link count: 1
+    end
+
+    it "renders the google link when the feature is enabled" do
+      Setting["feature.google_login"] = true
+
+      render_inline component
+
+      expect(page).to have_link "Google"
+      expect(page).to have_link count: 1
+    end
+
+    it "renders the wordpress link when the feature is enabled" do
+      Setting["feature.wordpress_login"] = true
+
+      render_inline component
+
+      expect(page).to have_link "Wordpress"
+      expect(page).to have_link count: 1
+    end
+  end
+end