mod_client_management: Report on longest lived token when grant does not expire E.g. for mod_http_oauth2 where by default the grant itself is unlimited, while refresh tokens are issued with one week lifetime, but are renewed with each use.

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summary: Log a message once per minute
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This module sends `-- MARK --` to the log once per minute. This may be
useful to give a sense of how busy the server is or see that logging and
timers are still working.