Zapr log levels don't align with glog/klog recommendations

[alvaroaleman]

The named debug log level of zap corresponds to the numeric value -1, which then gets inverted by zapr and thus corresponds toV(1). At the same time, the Kubernetes logging guidelines assume V(4) to be debug level and V(1) A reasonable default log level if you don't want verbosity: https://github.com/kubernetes/community/blob/905825353d20c57817806dd5aab242ea6c703024/contributors/devel/sig-instrumentation/logging.md#what-method-to-use

So the mapping between the two seems off, furthermore most users of zap are likely to not be aware that the log level is an int8 under the hood and can have values outside of the defined named set. We should find a way so that the named debug in zap corresponds to something resembling a debug log level in the glog/klog/logr universe.

[sbueringer]

Just want to mention that component-base uses zap for JSON logging under the hood (while they use klog for text). I didn't look up the details, but sounds like they are using zap in a way that the log levels are treated the same way between zap & klog.

(not saying that's the right "solution", just a data point)

component-base JSON zap implementation can be found here: https://github.com/kubernetes/component-base/blob/master/logs/json/json.go