peer review validation

[alee]

peer review requests shouldn't go through if there is no code / documentation to review

[alee]

@MarcoAJanssen suggests that we also run full publish validation on the model to ensure it has all the metadata fields required for publishing as well

[alee]

This is almost working, but not quite. When I request a peer review for a model that isn't publish()-able, it returns without requesting the peer review, but I don't see any of the appropriate / relevant error messages. Instead, I only see the relevant validation error messages if I request peer review again, e.g.: