DEV: Add dedicated category settings model - Part 1 (#20211)

This is the first in a multi-part change to move the custom fields to a new table. It includes:

- Adding a new CategorySetting model and corresponding table.
- Populating it with data from the category_custom_fields table.

db/migrate/20230207093514_create_category_settings.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class CreateCategorySettings < ActiveRecord::Migration[7.0]
+  def change
+    # Moving the custom fields in core into a dedicated table for
+    # better type casting, validations, etc.
+    create_table :category_settings do |t|
+      t.references :category, null: false, index: { unique: true }
+
+      t.boolean :require_topic_approval, null: true
+      t.boolean :require_reply_approval, null: true
+      t.integer :num_auto_bump_daily, null: true
+
+      t.timestamps
+    end
+  end
+end

db/migrate/20230208020404_populate_category_settings.rb

@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+class PopulateCategorySettings < ActiveRecord::Migration[7.0]
+  def up
+    execute(<<~SQL)
+      INSERT INTO
+        category_settings(
+          category_id,
+          require_topic_approval,
+          require_reply_approval,
+          num_auto_bump_daily,
+          created_at,
+          updated_at
+        )
+      SELECT
+        category_id,
+        MAX(
+          CASE WHEN (name = 'require_topic_approval')
+          THEN value ELSE NULL END
+        )::boolean AS require_topic_approval,
+        MAX(
+          CASE WHEN (name = 'require_reply_approval')
+          THEN value ELSE NULL END
+        )::boolean AS require_reply_approval,
+        MAX(
+          CASE WHEN (name = 'num_auto_bump_daily')
+          THEN value ELSE NULL END
+        )::integer AS num_auto_bump_daily,
+        NOW() AS created_at,
+        NOW() AS updated_at
+      FROM category_custom_fields
+      WHERE name IN (
+        'require_topic_approval',
+        'require_reply_approval',
+        'num_auto_bump_daily'
+      )
+      GROUP BY category_id;
+    SQL
+  end
+
+  def down
+    execute(<<~SQL)
+      TRUNCATE category_settings;
+    SQL
+  end
+end