A key absent from overrides, or present but not a parseIsoDate-parseable
ISO-8601 string, leaves that variable's static expiresAt untouched --
same "warn/skip, never guess" policy the rest of the generator uses for
malformed data. Contract-level expiresAt is never touched; only
variable-level expiresAt is in scope for override.
Applies
overridesonto a fresh copy ofcontracts-- every contract and every variable (and their nestedmetadata/extrarecords) is rebuilt into a new object, never the original reference, so the returned structure shares no mutable object identity withcontractsat any depth.