Firestore DocumentReference that will be fetched
Optionaloptions: UseDocumentOnceOptionsOptions to configure how the document is fetched
DocumentSnapshot, loading state, and error
undefined if document does not exist, is currently being fetched, or an error occurredtrue while fetching the document; false if the document was fetched successfully or an error occurredundefined if no error occurred
Returns the DocumentSnapshot of a Firestore DocumentReference. Does not update the DocumentSnapshot once initially fetched