Make it easier to add new omniauth buttons

Since we're using the exact same logic for all existing buttons, we can
just get the list of available ones and loop through them.

app/helpers/settings_helper.rb

@@ -1,4 +1,13 @@
 module SettingsHelper
+  def oauth_logins
+    [
+      (:twitter if feature?(:twitter_login)),
+      (:facebook if feature?(:facebook_login)),
+      (:google_oauth2 if feature?(:google_login)),
+      (:wordpress_oauth2 if feature?(:wordpress_login))
+    ].compact
+  end
+
   def feature?(name)
     setting["feature.#{name}"].presence || setting["process.#{name}"].presence
   end

app/views/devise/_omniauth_form.html.erb

@@ -6,38 +6,11 @@
       </div>
     </div>
 
-    <% if feature? :twitter_login %>
+    <% oauth_logins.each do |login| %>
       <div class="small-12 medium-6 large-4 column end">
-        <%= link_to t("omniauth.twitter.name"), user_twitter_omniauth_authorize_path,
+        <%= link_to t("omniauth.#{login}.name"), send("user_#{login}_omniauth_authorize_path"),
-                    title: t("omniauth.twitter.#{action}"),
+                    title: t("omniauth.#{login}.#{action}"),
-                    class: "button-twitter button expanded",
+                    class: "button-#{login.to_s.delete_suffix("_oauth2")} button expanded",
-                    method: :post %>
-      </div>
-    <% end %>
-
-    <% if feature? :facebook_login %>
-      <div class="small-12 medium-6 large-4 column end">
-        <%= link_to t("omniauth.facebook.name"), user_facebook_omniauth_authorize_path,
-                    title: t("omniauth.facebook.#{action}"),
-                    class: "button-facebook button expanded",
-                    method: :post %>
-      </div>
-    <% end %>
-
-    <% if feature? :google_login %>
-      <div class="small-12 medium-6 large-4 column end">
-        <%= link_to t("omniauth.google_oauth2.name"), user_google_oauth2_omniauth_authorize_path,
-                    title: t("omniauth.google_oauth2.#{action}"),
-                    class: "button-google button expanded",
-                    method: :post %>
-      </div>
-    <% end %>
-
-    <% if feature? :wordpress_login %>
-      <div class="small-12 medium-6 large-4 column end">
-        <%= link_to t("omniauth.wordpress_oauth2.name"), user_wordpress_oauth2_omniauth_authorize_path,
-                    title: t("omniauth.wordpress_oauth2.#{action}"),
-                    class: "button-wordpress button expanded",
                     method: :post %>
       </div>
     <% end %>