New migration strategy:

part.0144:
- Add new "enabled" field to PartParameterTemplate model
- Add new ContentType fields to the "PartParameterTemplate" and "PartParameter" models
- Data migration for existing "PartParameter" records

part.0145:
- Set NOT NULL constraints on new fields
- Remove the obsolete "part" field from the "PartParameter" model

src/backend/InvenTree/part/migrations/0144_auto_20251203_1045.py

@@ -0,0 +1,130 @@
+# Generated by Django 5.2.8 on 2025-12-03 10:45
+
+from django.db import migrations, models
+from django.db.models import deletion
+
+
+def update_parameter(apps, schema_editor):
+    """Data migration to update existing PartParameter records.
+    
+    - Set 'model_type' to the ContentType for 'part.Part'
+    - Set 'model_id' to the existing 'part_id' value
+    """
+
+    PartParameter = apps.get_model("part", "PartParameter")
+    Part = apps.get_model("part", "Part")
+    ContentType = apps.get_model("contenttypes", "ContentType")
+
+    part_content_type, created = ContentType.objects.get_or_create(
+        app_label="part",
+        model="partparameter",
+    )
+
+    parmeters_to_update = []
+
+    for parameter in PartParameter.objects.all():
+        parameter.model_type = part_content_type
+        parameter.model_id = parameter.part_id
+        parmeters_to_update.append(parameter)
+        
+    if len(parmeters_to_update) > 0:
+        
+        print(f"Updating {len(parmeters_to_update)} PartParameter records.")
+        
+        PartParameter.objects.bulk_update(
+            parmeters_to_update,
+            fields=["model_type", "model_id"],
+       )
+
+
+def reverse_update_parameter(apps, schema_editor):
+    """Reverse data migration to restore existing PartParameter records.
+    
+    - Set 'part_id' to the existing 'model_id' value
+    """
+
+    PartParameter = apps.get_model("part", "PartParameter")
+
+    parmeters_to_update = []
+
+    for parameter in PartParameter.objects.all():
+        parameter.part = parameter.model_id
+        parmeters_to_update.append(parameter)
+        
+    if len(parmeters_to_update) > 0:
+        
+        print(f"Reversing update of {len(parmeters_to_update)} PartParameter records.")
+        
+        PartParameter.objects.bulk_update(
+            parmeters_to_update,
+            fields=["part"],
+       )
+
+
+class Migration(migrations.Migration):
+    """Data migration for making the PartParameterTemplate and PartParameter models generic.
+    
+    - Add new fields to the "PartParameterTemplate" and "PartParameter" models
+    - Migrate existing data to populate the new fields
+    - Make the new fields non-nullable (if appropriate)
+    - Remove any obsolete fields (if necessary)
+    """
+
+    atomic = False
+
+    dependencies = [
+        ("part", "0143_alter_part_image"),
+    ]
+
+    operations = [
+        # Add the new "enabled" field to the PartParameterTemplate model
+        migrations.AddField(
+            model_name="partparametertemplate",
+            name="enabled",
+            field=models.BooleanField(
+                default=True,
+                help_text="Is this parameter template enabled?",
+                verbose_name="Enabled",
+            ),
+        ),
+        # Add the "model_type" field to the PartParmaeterTemplate model
+        migrations.AddField(
+            model_name="partparametertemplate",
+            name="model_type",
+            field=models.ForeignKey(
+                blank=True, null=True,
+                help_text="Target model type for this parameter template",
+                on_delete=deletion.SET_NULL,
+                to="contenttypes.contenttype",
+                verbose_name="Model type",
+            ),
+        ),
+        # Add the "model_type" field to the PartParameter model
+        # Note: This field is initially nullable, to allow existing records to remain valid.
+        migrations.AddField(
+            model_name="partparameter",
+            name="model_type",
+            field=models.ForeignKey(
+                blank=True, null=True,
+                on_delete=deletion.CASCADE,
+                to="contenttypes.contenttype",
+            ),
+        ),
+        # Add the "model_id" field to the PartParameter model
+        # Note: This field is initially nullable, to allow existing records to remain valid.
+        migrations.AddField(
+            model_name="partparameter",
+            name="model_id",
+            field=models.PositiveIntegerField(
+                blank=True, null=True,
+                help_text="ID of the target model for this parameter",
+                verbose_name="Model ID",
+            )
+        ),
+        # Migrate existing PartParameter records to populate the new fields
+        migrations.RunPython(
+            update_parameter,
+            reverse_code=reverse_update_parameter,
+        ),
+
+    ]

src/backend/InvenTree/part/migrations/0145_auto_20251203_1120.py

@@ -0,0 +1,42 @@
+# Generated by Django 5.2.8 on 2025-12-03 11:20
+
+from django.db import migrations, models
+from django.db.models import deletion
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("part", "0144_auto_20251203_1045"),
+    ]
+
+    operations = [
+        # Update the "model_type" field on the PartParameter model to be non-nullable
+        migrations.AlterField(
+            model_name="partparameter",
+            name="model_type",
+            field=models.ForeignKey(
+                on_delete=deletion.CASCADE,
+                to="contenttypes.contenttype",
+            ),
+        ),
+        # Update the "model_id" field on the PartParameter model to be non-nullable
+        migrations.AlterField(
+            model_name="partparameter",
+            name="model_id",
+            field=models.PositiveIntegerField(
+                help_text="ID of the target model for this parameter",
+                verbose_name="Model ID",
+            )
+        ),
+        # Remove the "unique_together" constraint on the PartParameter model
+        migrations.AlterUniqueTogether(
+            name="partparameter",
+            unique_together={('model_type', 'model_id', 'template')},
+        ),
+        # Remove the obsolete "part" field from the PartParameter model
+        migrations.RemoveField(
+            model_name="partparameter",
+            name="part",
+        ),
+    ]