mod_sasl2: Further break up success handling, into pre/post stream:features This allows us to enable mod_smacks after sending success, but before sending stream:features. Previously, the features were being calculated before SM was finalized on the session. We can't finalize SM before sending <success> because it may generate stanzas.

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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.