fix: change postal_code column from integer to string (#1585)

* fix: change postal_code column from integer to string

Allows non-numeric postal codes such as UK format (e.g. SW1A 2AA).
The integer column was silently dropping any alphanumeric input.

The migration is marked irreversible — once alphanumeric postal codes
exist, they cannot be safely cast back to integer.

* fix: update schema.rb, quote fixture postal_code, and add alphanumeric test

* fix: use conventional migration timestamp

db/migrate/20260428120000_change_postal_code_to_string_in_addresses.rb

@@ -0,0 +1,9 @@
+class ChangePostalCodeToStringInAddresses < ActiveRecord::Migration[7.2]
+  def up
+    change_column :addresses, :postal_code, :string, using: "postal_code::text"
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration, "postal_code was changed from integer to string; alphanumeric values cannot be cast back to integer"
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.2].define(version: 2026_04_12_120000) do
+ActiveRecord::Schema[7.2].define(version: 2026_04_28_120000) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "pgcrypto"
   enable_extension "plpgsql"
@@ -116,7 +116,7 @@ ActiveRecord::Schema[7.2].define(version: 2026_04_12_120000) do
     t.string "locality"
     t.string "region"
     t.string "country"
-    t.integer "postal_code"
+    t.string "postal_code"
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["addressable_type", "addressable_id"], name: "index_addresses_on_addressable"

test/fixtures/addresses.yml

@@ -4,6 +4,6 @@ one:
   locality: Los Angeles
   region: CA
   country: US
-  postal_code: 90001
+  postal_code: "90001"
   addressable: one
   addressable_type: Property

test/models/address_test.rb

@@ -39,6 +39,12 @@ class AddressTest < ActiveSupport::TestCase
     assert_equal "", address.to_s
   end
 
+  test "accepts alphanumeric postal codes" do
+    address = addresses(:one)
+    address.update!(postal_code: "SW1A 2AA")
+    assert_equal "SW1A 2AA", address.reload.postal_code
+  end
+
   test "can strip extras commas and spaces" do
     address = Address.new(
       line1: "123 Main St ,",