0.53.0
(feat): Add RequestOptions::additional_body_param (backed by additional_body_params) for sending
extra request body properties, such as undocumented or beta fields, without a new SDK release.
Properties are merged into the serialized body under their wire-format keys and override
generated fields with the same key. When an endpoint has no body, a JSON object containing only
the additional properties is sent. JSON and form-urlencoded bodies are supported; multipart and
raw bytes bodies are sent unchanged.