leak `api_key` value
Merge branch 'KAZOO-2620' of https://github.com/siplabs/kazoo into siplabs-KAZOO-2620
KAZOO-2620: created an API to retrieve just the api_key (possibly useful for a "show api key" popup), also added a query string parameter to include it in the standard response and made a system_config option to always include it
Merge branch 'siplabs-KAZOO-2620'