FIX: public sidebar sections belong to system user (#20972)

Before, public sidebar sections were belonging to admin. However, a better choice is system user.

db/migrate/20230404064728_system_user_for_public_sections.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class SystemUserForPublicSections < ActiveRecord::Migration[7.0]
+  def up
+    execute(<<-SQL)
+      UPDATE sidebar_sections
+      SET user_id = -1
+      WHERE public IS TRUE
+    SQL
+    execute(<<-SQL)
+      UPDATE sidebar_section_links
+      SET user_id = -1
+      FROM sidebar_sections
+      WHERE sidebar_sections.public IS TRUE
+        AND sidebar_section_links.sidebar_section_id = sidebar_sections.id
+    SQL
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end