[Bug] Add Utils for put header to gRPC Metadata to avoid duplicate data.

[dingshuangxi888]

Before Creating the Bug Report

• I found a bug, not just asking a question, which should be created in GitHub Discussions.

• I have searched the GitHub Issues and GitHub Discussions of this repository and believe that this is not a duplicate.

• I have confirmed that this bug belongs to the current repository, not other repositories of RocketMQ.

Runtime platform environment

Linux

RocketMQ version

develop

JDK Version

All Java version

Describe the Bug

The following code in org.apache.rocketmq.proxy.grpc.pipeline.AuthenticationPipeline#newContext will repeatedly insert AK information into the Metadata, which resulting in a memory leak.

if (StringUtils.isNotBlank(defaultAuthenticationContext.getUsername())) {
headers.put(GrpcConstants.AUTHORIZATION_AK, defaultAuthenticationContext.getUsername());
}

Steps to Reproduce

Send message with ACL 2.0 and gRPC client.

What Did You Expect to See?

The AK is unique in metadata no matter how many times the API calls.

What Did You See Instead?

The AK is unique in metadata no matter how many times the API calls.

Additional Context

No response