DEV: Upgrade Rails to 6.1.3.1 (#12688)

Rails 6.1.3.1 deprecates a few API and has some internal changes that break our tests suite, so this commit fixes all the deprecations and errors and now Discourse should be fully compatible with Rails 6.1.3.1. We also have a new release of the rails_failover gem that's compatible with Rails 6.1.3.1.

app/controllers/admin/backups_controller.rb

@@ -72,7 +72,7 @@ class Admin::BackupsController < Admin::AdminController
   def show
     if !EmailBackupToken.compare(current_user.id, params.fetch(:token))
       @error = I18n.t('download_backup_mailer.no_token')
-      return render template: 'admin/backups/show.html.erb', layout: 'no_ember', status: 422
+      return render layout: 'no_ember', status: 422, formats: [:html]
     end
 
     store = BackupRestore::BackupStore.create

app/controllers/metadata_controller.rb

@@ -11,7 +11,7 @@ class MetadataController < ApplicationController
 
   def opensearch
     expires_in 1.minutes
-    render template: "metadata/opensearch.xml"
+    render template: "metadata/opensearch", formats: [:xml]
   end
 
   def app_association_android

app/controllers/static_controller.rb

@@ -29,7 +29,7 @@ class StaticController < ApplicationController
     if map.has_key?(@page)
       site_setting_key = map[@page][:redirect]
       url = SiteSetting.get(site_setting_key)
-      return redirect_to(url) unless url.blank?
+      return redirect_to(url) if url.present?
     end
 
     # The /guidelines route ALWAYS shows our FAQ, ignoring the faq_url site setting.
@@ -70,12 +70,8 @@ class StaticController < ApplicationController
       cookies[:email] = { value: params[:email], expires: 1.day.from_now }
     end
 
-    file = "static/#{@page}.#{I18n.locale}"
-    file = "static/#{@page}.en" if lookup_context.find_all("#{file}.html").empty?
-    file = "static/#{@page}"    if lookup_context.find_all("#{file}.html").empty?
-
-    if lookup_context.find_all("#{file}.html").any?
-      render file, layout: !request.xhr?, formats: [:html]
+    if lookup_context.find_all("static/#{@page}").any?
+      render "static/#{@page}", layout: !request.xhr?, formats: [:html]
       return
     end