add a notification message model

part of #2282

InvenTree/common/migrations/0013_notificationmessage.py

@@ -0,0 +1,33 @@
+# Generated by Django 3.2.5 on 2021-11-27 14:51
+
+from django.conf import settings
+from django.db import migrations, models
+import django.db.models.deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ('contenttypes', '0002_remove_content_type_name'),
+        ('common', '0012_notificationentry'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='NotificationMessage',
+            fields=[
+                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('target_object_id', models.PositiveIntegerField()),
+                ('source_object_id', models.PositiveIntegerField(blank=True, null=True)),
+                ('category', models.CharField(max_length=250)),
+                ('name', models.CharField(max_length=250)),
+                ('message', models.CharField(blank=True, max_length=250, null=True)),
+                ('creation', models.DateTimeField(auto_now=True)),
+                ('read', models.BooleanField(default=False)),
+                ('source_content_type', models.ForeignKey(blank=True, null=True, on_delete=django.db.models.deletion.SET_NULL, related_name='notification_source', to='contenttypes.contenttype')),
+                ('target_content_type', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='notification_target', to='contenttypes.contenttype')),
+                ('user', models.ForeignKey(blank=True, help_text='User', null=True, on_delete=django.db.models.deletion.CASCADE, to=settings.AUTH_USER_MODEL, verbose_name='User')),
+            ],
+        ),
+    ]