Useful for excluding /ping endpoint to reduce log volume.
This is somewhat more verbose than a simple bool to disable logging of
the `/ping` endpoint.
Perhaps better to add `-silence-ping-logging` bool flag to `options.go` and
pass in the `/ping` endpoint as part of `logger` declaration in `options.go`.
Could be extended into a slice of paths similar to go-gin's `SkipPaths`:
https://github.com/gin-gonic/gin/blob/master/logger.go#L46
Add ability to silence logging of requests to /ping endpoint, reducing
log clutter
Pros:
- Don't have to change all handlers to set/not set silent ping logging
- Don't have to duplicate `loggingHandler` (this could be preferable yet)
Cons:
- Leaking oauth2proxy logic into `package logger`
- Defining default pingPath in two locations
Alternative:
- Add generic exclude path to `logger.go` and pass in `/ping`.
