I think that in order to build fully federated/distributed web applications, we need to generalize the use of the IDUrlField instead of the ForeignKey relations in our packages models.

In the case of the conversation packages, both author_user properties in both the Conversation and Message models should be switched to IDUrlField.

I will need it for Coopstarter by the way, as any User of any instances should be able to comment and give feedback about a resource.

@matthieu @sylvain what do you think ?