Refacto edit method for content controller and enable custom user guide link

app/models/preference_sections/header_section.rb

@@ -0,0 +1,15 @@
+module PreferenceSections
+  class HeaderSection
+    def name
+      I18n.t('admin.contents.edit.header')
+    end
+
+    def preferences
+      [
+        :logo,
+        :logo_mobile,
+        :logo_mobile_svg
+      ]
+    end
+  end
+end