mod_prometheus: Invoke stats collection if in 'manual' mode Since 10d13e0554f9 a special value for statistics_interval "manual" exists, where a module is expected to invoke processing in connection to collection of stats. This makes internal collection and exporting to Prometheus happens at the same time with no chance of timers getting out of sync.

Introduction
============

This module checks the IP address of newly registered users against a
DNS block list. If a positive match is found, it gets logged.

Configuration
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  Option              Type     Default
  ------------------- -------- ------------
  registration\_rbl   string   *Required*