feat: remove old microbachelor's coaching external IDs

The microbachelor coaching facility has been deprecated and the external
IDs are no longer supported. Remove existing ones from the DB.

FIXES: APER-2941

openedx/core/djangoapps/external_user_ids/migrations/0007_remove_mbcoaching_extids.py

@@ -0,0 +1,26 @@
+# Generated by Django 3.2.23 on 2023-12-04 18:48
+"""Deletes instances of deprecated mb_coaching external ID type"""
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("external_user_ids", "0006_auto_20230808_0944"),
+    ]
+
+    mb_coaching_type_name = "mb_coaching"
+
+    def delete_ids(apps, schema_editor):
+        # The
+        ExternalIdType = apps.get_model("external_user_ids", "ExternalIdType")
+        mb_coaching_type_id = ExternalIdType.objects.get(
+            name=Migration.mb_coaching_type_name
+        ).id
+
+        ExternalId = apps.get_model("external_user_ids", "ExternalId")
+        ExternalId.objects.filter(external_id_type=mb_coaching_type_id).delete()
+
+    operations = [
+        migrations.RunPython(delete_ids, reverse_code=migrations.RunPython.noop)
+    ]