add RequestStore gem, support universal only param for api endpoints (fixes #4068)

app/controllers/application_controller.rb

@@ -10,6 +10,7 @@ class ApplicationController < ActionController::Base
   before_action :api_check
   before_action :set_safe_mode
   before_action :set_variant
+  before_action :track_only_param
   # before_action :secure_cookies_check
   layout "default"
   helper_method :show_moderation_notice?
@@ -48,6 +49,12 @@ class ApplicationController < ActionController::Base
     end
   end
 
+  def track_only_param
+    if params[:only]
+      RequestStore[:only_param] = params[:only].split(/,/)
+    end
+  end
+
   def api_check
     if !CurrentUser.is_anonymous? && !request.get? && !request.head?
       if CurrentUser.user.token_bucket.nil?

app/controllers/post_versions_controller.rb

@@ -7,7 +7,7 @@ class PostVersionsController < ApplicationController
     @post_versions = PostArchive.includes(:updater, post: [:versions]).search(search_params).paginate(params[:page], :limit => params[:limit], :search_count => params[:search])
     respond_with(@post_versions) do |format|
       format.xml do
-        render :xml => @post_versions.to_xml(:root => "post-versions")
+        render xml: @post_versions.to_xml(root: "post-versions")
       end
     end
   end

app/controllers/posts_controller.rb

@@ -14,7 +14,7 @@ class PostsController < ApplicationController
       respond_with(@posts) do |format|
         format.atom
         format.xml do
-          render :xml => @posts.to_xml(:root => "posts")
+          render xml: @posts.to_xml(root: "posts")
         end
       end
     end