Better visibility on ingress errors

[gak]

logger.Debugf("bad request: %s", err.Error()) in ingress handler does not mention the verb involved and is difficult to know which request has failed in production.

This is related to a webhook coming in and erroring, but the user can not observe exactly why/how it failed. This is also very handy when you have little feedback from a webhook provider.

[jiyoonie9]

example error message:
bad request: 0:0: expected array, got string

[alecthomas]

We should replace:

	logger.Debugf("%s %s", r.Method, r.URL.Path)

with something like the following, so that all log messages have this context:

	logger = logger.Scope(fmt.Sprintf("%s %s", r.Method, r.URL.Path))