replace ammo added on with purchased on

priv/repo/migrations/20221119192131_add_purchase_date_to_ammo_group.exs

@@ -0,0 +1,19 @@
+defmodule Cannery.Repo.Migrations.AddPurchaseDateToAmmoGroup do
+  use Ecto.Migration
+
+  def up do
+    alter table(:ammo_groups) do
+      add :purchased_on, :date
+    end
+
+    flush()
+
+    execute("UPDATE ammo_groups SET purchased_on = inserted_at::DATE WHERE purchased_on IS NULL")
+  end
+
+  def down do
+    alter table(:ammo_groups) do
+      remove :purchased_on
+    end
+  end
+end