Add datetime: null when an item has start_datetime and end_datetime but no datetime.#391

krisaoe wants to merge 1 commit intostac-utils:mainstac-utils/pgstac:mainfrom

krisaoe:fix/allow-datetime-null-if-range-existskrisaoe/pgstac:fix/allow-datetime-null-if-range-existsCopy head branch name to clipboard