discardLocalChanges must be true: the un-pushed local changes are
taken out of the queue and returned to the caller instead of being sent
again. There is no non-discarding form — the server refused those changes,
and re-presenting them is what wedged the document in the first place.
It is spelled out at the call site so the data loss is never implicit.
OptionalinitialinitialPresence is the presence to attach with. Defaults to the
document's current presence, so a recovery keeps the cursor the user is
holding: presence is not what the server refused.
ResyncOptionsare the options of Client.resync.