Dubbo-Admin的测试功能，是否可以增加设置RpcContext.getClientAttachment().setAttachment参数的功能

系统中有部分接口是通过RPC上下文传递当前登录用户的标识，使用Dubbo-Admin测试这类接口的时候，没办法设置当前登录用户，是否可以增加设置的入口

Start by locating Dubbo-Admin's test feature and the handling around RpcContext.getClientAttachment().setAttachment. Determine how the test request is assembled and where an attachment-setting entry point belongs. Done means users can provide the current-user identifier when testing interfaces that read it from the RPC context.

Written by the indexing model from the issue text.