多言語化の基盤作り (#55) (#421)

Reviewed-on: #421
Co-authored-by: miteruzo <miteruzo@naver.com>

backend/db/migrate/20260922013000_create_regions.rb

@@ -0,0 +1,25 @@
+class CreateRegions < ActiveRecord::Migration[8.0]
+  def up
+    create_table :regions, id: { type: :integer, limit: 2 }, primary_key: :code do |t|
+      t.column :alpha_code, 'CHAR(2)'
+      t.string :name, null: false
+      t.datetime :deprecated_at, index: true
+      t.datetime :created_at, null: false
+
+      t.check_constraint "REGEXP_LIKE(alpha_code, '^[A-Z]{2}$', 'c')",
+                         name: 'regions_alpha_code_check'
+      t.index [:alpha_code], unique: true
+    end
+
+    execute <<~SQL
+      INSERT INTO
+        regions(code, alpha_code, name, created_at)
+      VALUES
+        (392, 'JP', '日本国', #{ connection.quote Time.current })
+    SQL
+  end
+
+  def down
+    drop_table :regions
+  end
+end