Setting for original message upload_to

Also changed the default from "messages" to separate-by-date
directories "mailbox_messages/%Y/%m/%d/"

django_mailbox/migrations/0010_alter_message_eml.py

@@ -0,0 +1,19 @@
+# Generated by Django 5.1.6 on 2025-12-18 12:54
+
+import django_mailbox.utils
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('django_mailbox', '0009_alter_message_eml'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='message',
+            name='eml',
+            field=models.FileField(blank=True, help_text='Original full content of message', null=True, upload_to=django_mailbox.utils.get_original_message_save_path, verbose_name='Raw message contents'),
+        ),
+    ]