mod_http_oauth2: Enforce the registered grant types Thus a client can limit itself to certain grant types. Not sure if this prevents any attacks, but what was the point of including this in the registration if it was not going to be enforced? This became easier to do with client_id being available earlier.

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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.