The revised logging emits one log entry at the start of
round-tripping ("Request") and another at the end ("Response"). This avoids the
risk that related output gets interleaved by other output.
No API changes are necessary. A contextual logger is picked up from the context
of the request that is being handled. The verbosity level of that logger is
checked to determine what is supposed to be logged. This enables reducing log
details on a by-request basis by storing a `logger.V(1)` in the context of the
request.
As before, logging only gets injected into request processing at -v6 or higher,
so normally there is no additional overhead.
Kubernetes-commit: a85f489b28d3b0ef82dffb267b6145c73c2d0e33
