Instance helper to replace site title helper (#2038)

* Move site title helper to instance helper (name change only)

* Remove newline in <title> tag

* Add site_hostname helper method to wrap up local_domain value

* Use site_hostname helper in places that need local_domain value

app/helpers/instance_helper.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module InstanceHelper
+  def site_title
+    Setting.site_title.to_s
+  end
+
+  def site_hostname
+    Rails.configuration.x.local_domain
+  end
+end

app/helpers/site_title_helper.rb

@@ -1,7 +0,0 @@
-# frozen_string_literal: true
-
-module SiteTitleHelper
-  def site_title
-    Setting.site_title.to_s
-  end
-end