Private snap without mandatory fields such as support URL set can be made public without adding such fields

[Gareth Woolridge]

I created a snap and uploaded to store and was unable to publish (as expected) without setting mandatory fields such as Support URL.

As I was using this snap as a learning exercise I switched it to private to investigate releasing to channels etc and published as private snap without being requested to set Support URL.

I then switched the snap to public and got no request to set the mandatory Support URL field at this stage, presumably as the snap was already in a published state.