Investigate "ValidationError {'release_date': ['This field cannot be blank.']}" during import

This was reported on reddit https://www.reddit.com/r/Funkwhale/comments/964a3n/awesome_project/

The release_date field should not be mandatory.

changed milestone to %0.17

mentioned in commit 71c70cee

mentioned in merge request !380 (merged)

assigned to @eliotberriot

closed via commit 71c70cee

mentioned in commit 3f9bf9af

closed via merge request !380 (merged)

mentioned in commit 03153efc

mentioned in commit 14774f39