feat: add gzip as content-encoding

The engine is introducing a new feature allowing to optionally compress request
payloads (ie. POST/PUT body, http or https).

To test it:

Perform a `saveObject` with the content encoded with GZIP
Don't forget to add: `"Content-Encoding: gzip"` as a header.

We will discuss a specification for a more detailed implementation.
Like adding a `enableGZIP` flag in client's configuration.

该 issue 未指明文件或测试；首先在 TypeScript 客户端中定位 saveObject 请求路径，并复现所描述的 gzip 请求。开始前，与维护者确认实现和配置规范；完成的定义是已验证约定的可选 gzip content-encoding 行为。

由索引模型根据 Issue 内容生成。