mod_http_oauth2: Enforce response type encoded in client_id The client promises to only use this response type, so we should hold them to that. This makes it fail earlier if the response type is disabled or the client is trying to use one that it promised not to use. Better than failing after login and consent.

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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.