support multiple file operations

build instructions:
```
https://github.com/0chain/zs3server
docker run --rm -v $PWD:/minio -v go-modules:/go/pkg/mod --workdir=/minio golang:1.18 go build
cd environment
make dev
```

zs3server improvements
```
* putObject -> multiple files
* getObject --> multiple files
* removeObject -> multiple files
```

The issue is about extending S3-compatible API endpoints (putObject, getObject, removeObject) to handle multiple files. Start by examining the existing handler implementations for these operations in the codebase, likely in a directory like `handlers/` or `api/`. Look for how single-file operations are currently structured. The build instructions suggest using Docker and a Make target (`make dev`) for local development. Understanding the S3 protocol's expectations for batch operations will be key. 'Done' means the server can accept, process, and respond to requests for multiple files for each listed operation.

Escrito por el modelo de indexación a partir del texto del issue.