Enum value from request cannot be injected directly in response serializer

[AMontagu]

This is an edge case but it is actually happening.

I created a branch name issue/requestDataCannotBeInjectedDirectlyInSerializerData that have a test that fail because of the issue.

I could fix it but their is different way of doing it and we may not want to fix it but only document it.

The example:

@grpc_action(
        request=[{"name": "char_choices", "type": EnumModel.MyTestStrEnum}],
        response=EnumServiceSerializerOnlyOneField,
        use_generation_plugins=[InMessageWrappedEnumGenerationPlugin()],
        override_default_generation_plugins=True,
    )
    async def BasicEnumRequestInSerializerOut(self, request, context):
        data = {"char_choices": request.char_choices}
        # data = {"char_choices": EnumModel.MyTestStrEnum.values[request.char_choices - 1]}
        serializer = EnumServiceSerializerOnlyOneField(data=data)
        serializer.is_valid(raise_exception=True)

        """
        message = EnumServiceOnlyOneFieldResponse(char_choices=request.char_choices)
        return message
        """
        return serializer.message

This action fail.

When using either data = {"char_choices": EnumModel.MyTestStrEnum.values[request.char_choices - 1]} or message = EnumServiceOnlyOneFieldResponse(char_choices=request.char_choices) it fix the issue but it's a manual behavior that the user need to know and need to be documented.

An other way is to check in proto_serializers.BaseProtoSerializer.data_to_message if the data[field_name] is an integer then we do not try to map the data but it may create issue with integer enum.

It also possible to add a kwargs argument to the serializer to stop conversion for specified field.

What do you think @Giiltham @legau ? I can fix it I just need to be agree on the fix we implement