add message and comment

message/serializers.py

@@ -0,0 +1,19 @@
+from submission.serializers import SubmissionSafeModelSerializer
+from utils.api import UsernameSerializer, serializers
+from .models import Message
+
+
+
+class MessageSerializer(serializers.ModelSerializer):
+    sender = UsernameSerializer()
+    submission = SubmissionSafeModelSerializer()
+
+    class Meta:
+        model = Message
+        exclude = ["recipient"]
+
+
+class CreateMessageSerializer(serializers.Serializer):
+    recipient = serializers.IntegerField()
+    submission = serializers.CharField()
+    message = serializers.CharField()