fix: refactor index_together to indexes for Django 5.2 support (IV) (#36716)

* fix: refactor index_together to indexes for Django 5.2 support

* fix: fix quality issues

lms/djangoapps/grades/migrations/0022_rename_persistentsubsectiongrade_first_attempted_course_id_user_id_first_course_id_user_id_idx_and_m.py

@@ -0,0 +1,23 @@
+# Generated by Django 4.2.20 on 2025-05-14 05:53
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('grades', '0021_rename_persistentcoursegrade_passed_timestamp_course_id_passed_timestamp_course_id_idx_and_more'),
+    ]
+
+    operations = [
+        migrations.RenameIndex(
+            model_name='persistentsubsectiongrade',
+            new_name='first_course_id_user_id_idx',
+            old_fields=('first_attempted', 'course_id', 'user_id'),
+        ),
+        migrations.RenameIndex(
+            model_name='persistentsubsectiongrade',
+            new_name='course_id_usage_key_idx',
+            old_fields=('modified', 'course_id', 'usage_key'),
+        ),
+    ]

lms/djangoapps/grades/models.py

@@ -315,9 +315,15 @@ class PersistentSubsectionGrade(TimeStampedModel):
         #   in a course
         # (first_attempted, course_id, user_id): find all attempted subsections in a course for a user
         # (first_attempted, course_id): find all attempted subsections in a course for all users
-        index_together = [
-            ('modified', 'course_id', 'usage_key'),
-            ('first_attempted', 'course_id', 'user_id')
+        indexes = [
+            models.Index(
+                fields=['modified', 'course_id', 'usage_key'],
+                name="course_id_usage_key_idx"
+            ),
+            models.Index(
+                fields=['first_attempted', 'course_id', 'user_id'],
+                name="first_course_id_user_id_idx"
+            ),
         ]
 
     # primary key will need to be large for this table