Use status code 102 while submission is in progress.
Return wether or not the pod version is published with status code 102 or 200.
Report a 404 when a pod or version can't be found.
Remove pod_versions.state column.
Re-instate pod_versions.state column and store there wether or not it's published.
Set default state of a pod version to 'submitted'.
Move pod_versions.state to submission_jobs and add published flag back.