Update human_readable_id field in Order model

Alter the `human_readable_id` field to use a custom generator function and ensure uniqueness. This improves the readability and integrity of order identifiers.

core/migrations/0019_alter_order_human_readable_id.py

@@ -0,0 +1,19 @@
+# Generated by Django 5.1.8 on 2025-05-06 14:01
+
+import core.utils
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('core', '0018_alter_order_human_readable_id'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='order',
+            name='human_readable_id',
+            field=models.CharField(default=core.utils.generate_human_readable_id, help_text='a human-readable identifier for the order', max_length=8, unique=True, verbose_name='human readable id'),
+        ),
+    ]