DEV: Create permanent version of moved_posts table from PostMover class (#29664)

This is a very simple change, which creates a permanent table in the DB, rather than generating a temporary table when moving posts. This change is about capturing data and any usage will appear in a follow-up.

I did include a new column created_new_topic in the new table, so that it can be easily audited without having to compare destination topic created_at with moved_post records.

db/migrate/20241108154026_create_moved_posts.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class CreateMovedPosts < ActiveRecord::Migration[7.1]
+  def change
+    create_table :moved_posts do |t|
+      t.bigint :old_topic_id, null: false, index: true
+      t.bigint :old_post_id, null: false, index: true
+      t.bigint :old_post_number, null: false, index: true
+      t.bigint :new_topic_id, null: false, index: true
+      t.string :new_topic_title, null: false
+      t.bigint :new_post_id, null: false, index: true
+      t.bigint :new_post_number, null: false
+      t.boolean :created_new_topic, null: false, default: false
+      t.timestamps
+    end
+  end
+end