chore: rename ComponentVersionMedia DB column _key -> path

Renames the underlying database column for ComponentVersionMedia.path
from the legacy '_key' name to 'path'. Uses SeparateDatabaseAndState
with RunSQL (RENAME COLUMN) for SQLite/MySQL compatibility.

Part of: #322

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: kdmccormick

src/openedx_content/applets/components/models.py

@@ -243,8 +243,8 @@ class ComponentVersionMedia(models.Model):
     media = models.ForeignKey(Media, on_delete=models.RESTRICT)
 
     # path is a local file-path-like identifier for the media within a
-    # ComponentVersion. The DB column is still named "_key" (renamed later).
-    path = ref_field(db_column="_key")
+    # ComponentVersion.
+    path = ref_field()
 
     class Meta:
         constraints = [

src/openedx_content/migrations/0017_rename_componentversionmedia_db_column_key_to_path.py

@@ -0,0 +1,37 @@
+from django.db import migrations
+
+import openedx_django_lib.fields
+
+
+class Migration(migrations.Migration):
+    """
+    Rename the underlying DB column for ComponentVersionMedia.path from
+    '_key' to 'path'. Uses SeparateDatabaseAndState with RunSQL for
+    SQLite/MySQL compatibility. The table is named
+    'openedx_content_componentversionmedia' (Django default).
+    """
+
+    dependencies = [
+        ('openedx_content', '0016_rename_componentversionmedia_key_to_path'),
+    ]
+
+    operations = [
+        migrations.SeparateDatabaseAndState(
+            state_operations=[
+                migrations.AlterField(
+                    model_name='componentversionmedia',
+                    name='path',
+                    field=openedx_django_lib.fields.MultiCollationCharField(
+                        db_collations={'mysql': 'utf8mb4_bin', 'sqlite': 'BINARY'},
+                        max_length=500,
+                    ),
+                ),
+            ],
+            database_operations=[
+                migrations.RunSQL(
+                    sql='ALTER TABLE openedx_content_componentversionmedia RENAME COLUMN _key TO path',
+                    reverse_sql='ALTER TABLE openedx_content_componentversionmedia RENAME COLUMN path TO _key',
+                ),
+            ],
+        ),
+    ]