Migration bug fix 2 (#4977)

* Additional migration fix:

- In #4961 we did not notice that the migration files had been renamed
- There is still a chance that a production db (running from master) has a corrupted set of migrations
- Check if the duplicate columns already exist
- If they do, delete them first

* Typo fix

* Add PR reference

InvenTree/part/migrations/0112_auto_20230525_1606.py

@@ -1,8 +1,40 @@
 # Generated by Django 3.2.19 on 2023-05-31 12:05
 
+from django.core.exceptions import FieldDoesNotExist
 from django.db import migrations, models
 
 
+def delete_columns(apps, schema_editor):
+    """Hack method to delete columns (if they already exist).
+
+    Due to an improper set of migrations merges,
+    there may exist a situation where the columns (defined in the migrations below) already exist.
+
+    In this case, we want to delete the columns, and then re-add them.
+
+    Original error: https://github.com/inventree/InvenTree/pull/4898
+    Attempted fix: https://github.com/inventree/InvenTree/pull/4961
+    This fix: https://github.com/inventree/InvenTree/pull/4977
+    """
+
+    PartParameterTemplate = apps.get_model('part', 'PartParameterTemplate')
+
+    # Check if the 'checkbox' column exists
+    try:
+        print("Checking for column 'checkbox' in table 'part_partparametertemplate'")
+        PartParameterTemplate._meta.get_field('checkbox')
+        schema_editor.execute("ALTER TABLE part_partparametertemplate DROP COLUMN checkbox;")
+    except (AttributeError, FieldDoesNotExist):
+        print("Column 'checkbox' does not exist (skipping)")
+
+    try:
+        print("Checking for column 'choices' in table 'part_partparametertemplate'")
+        PartParameterTemplate._meta.get_field('choices')
+        schema_editor.execute("ALTER TABLE part_partparametertemplate DROP COLUMN choices;")
+    except (AttributeError, FieldDoesNotExist):
+        print("Column 'choices' does not exist (skipping)")
+
+
 class Migration(migrations.Migration):
 
     dependencies = [
@@ -10,6 +42,9 @@ class Migration(migrations.Migration):
     ]
 
     operations = [
+        migrations.RunPython(
+            delete_columns, reverse_code=migrations.RunPython.noop
+        ),
         migrations.AddField(
             model_name='partparametertemplate',
             name='checkbox',