ATS should keep a read-only copy of the original client request

[shinrich]

The client request data may be updated by plugins during the processing of the transaction. This updating means by the time logging occurs, there may be no clean version of the original request. This issue was identified among other places in issue #4697.

The unmapped version of the logging fields help, but even those fields may be changed from the original by plugins that trigger on the read request hook.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. Marking it stale to flag it for further consideration by the community.