the command result must be the new object instead of the old one.
the modifier document.
(update: StringAdd).self
(update: StringFormat).self
(update: ArrowAssoc[Update]).x
(Since version 2.10.0) Use leftOfArrow
instead
(update: Ensuring[Update]).x
(Since version 2.10.0) Use resultOfEnsuring
instead
Update (part of a FindAndModify command).
the modifier document.
the command result must be the new object instead of the old one.
(Since version 0.11.0) consider using reactivemongo.api.commands.FindAndModifyCommand instead