Support query the currently active global transaction

## Why you need it?
Is your feature request related to a problem? Please describe in details
After modify the TC as springboot project, We are supposed to add some openapi.
the current issue is to require someone to support query the currently active global transaction by openapi.
If you want to support it, please comment "Please assign it to me" is this issue.

完成SpringBoot改造之后，需要提供一些对外的接口，用于查询当前活动的全局事务
如果你有兴趣支持这个问题的话, 请在下方留言 Please assign it to me

## How it could be?
A clear and concise description of what you want to happen. You can explain more about input of the feature, and output of it.

## Other related information
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