rename serializer field file to recorded_file with source='file' to match recording client payload

apps/course/serializers/online.py

@@ -53,14 +53,14 @@ class LiveSessionRecordedFileSerializer(serializers.Serializer):
 
 
 class LiveSessionRecordingSerializer(serializers.Serializer):
-    file = FileFieldSerializer(required=True)
+    recorded_file = FileFieldSerializer(required=True, source='file')
     title = serializers.CharField(required=False, max_length=255, allow_blank=True)
     recording_type = serializers.ChoiceField(choices=['voice', 'video'], required=False, default='video')
     file_time = serializers.DurationField(required=False, allow_null=True)
 
-    def validate_file(self, value):
+    def validate_recorded_file(self, value):
         if not value:
-            raise serializers.ValidationError("file is required.")
+            raise serializers.ValidationError("recorded_file is required.")
         return value
 
     def validate_title(self, value):