[Enhancement] Add namespace in java client

### Before Creating the Enhancement Request

- [X] I have confirmed that this should be classified as an enhancement rather than a bug/feature.

### Programming Language of the Client

Java

### Summary

Add namespace in java client.

### Motivation

For the purpose for the future namespace feature.

### Describe the Solution You'd Like

Add namespace in ClientConfiguration.

### Describe Alternatives You've Considered

No

### Additional Context

_No response_