adds a "link" field to the InvenTree attachment model

- Allows attachments to also serve as links to external files

InvenTree/order/migrations/0053_auto_20211128_0151.py

@@ -0,0 +1,35 @@
+# Generated by Django 3.2.5 on 2021-11-28 01:51
+
+import InvenTree.fields
+import InvenTree.models
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('order', '0052_auto_20211014_0631'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='purchaseorderattachment',
+            name='link',
+            field=InvenTree.fields.InvenTreeURLField(blank=True, help_text='Link to external URL', null=True, verbose_name='Link'),
+        ),
+        migrations.AddField(
+            model_name='salesorderattachment',
+            name='link',
+            field=InvenTree.fields.InvenTreeURLField(blank=True, help_text='Link to external URL', null=True, verbose_name='Link'),
+        ),
+        migrations.AlterField(
+            model_name='purchaseorderattachment',
+            name='attachment',
+            field=models.FileField(blank=True, help_text='Select file to attach', null=True, upload_to=InvenTree.models.rename_attachment, verbose_name='Attachment'),
+        ),
+        migrations.AlterField(
+            model_name='salesorderattachment',
+            name='attachment',
+            field=models.FileField(blank=True, help_text='Select file to attach', null=True, upload_to=InvenTree.models.rename_attachment, verbose_name='Attachment'),
+        ),
+    ]