Auto assign username

api/v1/serializers/user.py

@@ -55,6 +55,9 @@ class UserSerializer(serializers.ModelSerializer):
         )
 
     def create(self, validated_data):
+        username = validated_data.get('username', None)
+        if not username:
+            validated_data['username'] = validated_data['email']
         instance = super().create(validated_data)
         if not instance.password:
             password = User.objects.make_random_password()