Add a new Authorize Log Fields option for logging the number of groups
removed during JWT groups filtering. This will be enabled by default.
Additionally, when the log level is Debug (or more verbose), store and
log the IDs of any groups removed during JWT groups filtering.
Currently the 'user-id' field of the authorize logs is empty for
requests authenticated via a service account, as there is no associated
User object. Instead, populate this log field directly from the the
sessionOrServiceAccount value, to handle both types of user.
* config: add customization options for logging
* config: validate log fields
* proxy: add support for logging http request headers
* log subset of headers
* add support for logging the http query
* fix test name
* use strings.Cut, add unit tests
