Similarily to categories and rooms,
the edit product screen is reused as a new-room screen,
which is especially easy, because the user is unable to select
the product id themselves.
NOTE: the dynamic value-unit input is still missing some "subunits"
The view product screen has links to the edit product page,
the view parent page (if available) and a not yet functional
view children screen.
NOTE: The parent product display should be restricted in width,
and the screen is missing value/unit information.
