FEATURE: ability to reorder links in custom sidebar sections (#20626)

Drag and drop to reorder custom sidebar sections

db/migrate/20230307051200_add_position_to_sidebar_section_links.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class AddPositionToSidebarSectionLinks < ActiveRecord::Migration[7.0]
+  def change
+    add_column :sidebar_section_links, :position, :integer, default: 0, null: false
+    execute "UPDATE sidebar_section_links SET position = id"
+    add_index :sidebar_section_links,
+              %i[user_id sidebar_section_id position],
+              unique: true,
+              name: "links_user_id_section_id_position"
+  end
+end