Build a Snapshot wrapper for one field of a snapshot object.
Returns undefined when no snapshot exists for the id at all (first sync),
or { value } when the snapshot exists — value may itself be undefined
if the field is a legitimate "no value" sentinel (e.g. Linear's priority).
Build a Snapshot wrapper for one field of a snapshot object.
Returns
undefinedwhen no snapshot exists for the id at all (first sync), or{ value }when the snapshot exists —valuemay itself beundefinedif the field is a legitimate "no value" sentinel (e.g. Linear's priority).