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## 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.