do not cascade delete ProcessDatasetSet when deleting DatasetSet

arkindex/process/migrations/0032_processdatasetset_model.py

@@ -19,7 +19,7 @@ class Migration(migrations.Migration):
             fields=[
                 ("id", models.UUIDField(default=uuid.uuid4, editable=False, primary_key=True, serialize=False)),
                 ("process", models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name="process_sets", to="process.process")),
-                ("set", models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name="process_sets", to="training.datasetset")),
+                ("set", models.ForeignKey(on_delete=django.db.models.deletion.DO_NOTHING, related_name="process_sets", to="training.datasetset")),
             ],
         ),
         migrations.AddConstraint(

arkindex/process/models.py

@@ -471,7 +471,7 @@ class ProcessDatasetSet(models.Model):
     """
     id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
     process = models.ForeignKey(Process, on_delete=models.CASCADE, related_name="process_sets")
-    set = models.ForeignKey("training.DatasetSet", on_delete=models.CASCADE, related_name="process_sets")
+    set = models.ForeignKey("training.DatasetSet", on_delete=models.DO_NOTHING, related_name="process_sets")
 
     class Meta:
         constraints = [