Streamline distribution modelling
CLOSED - DUPLICATE
All forms of Distributions now have a "repository" field for use in auto-distribution, however, they are defined separately on RepositoryVersionDistribution and PublicationDistribution.
We need to unify these and put the "repository" field on base distribution instead. In addition to being cleaner it would also make it possible to list auto-distribute targets from the repository model.
This is very difficult to migrate due to the nature of abstract classes and the fact that the models are defined in separate apps.