1.57.13
(fix): Calling a SetXxx setter on a value copy of a request or model type no longer
changes the JSON of the value it was copied from. The private explicitFields
bitmask is reached through a pointer, so a plain struct assignment aliased it and
require mutated it in place, making every explicit-field bit set on one copy
visible in all of them (e.g. copied.SetOptions(...) added "options":null to
the original’s body). The bitmask is now replaced rather than mutated, so each
copy gets its own on first write.