chg: changing logic to look for CLEAR token in title.

[AlanBCole]

Now the data flow is:

1. If CLEAR token: (show no alert)
   • set rave_alerts_active_event to 0.
   • set rave_alerts_display to 0.
   • log clear event.
2. If ACTIVE token: (still not showing anything)
   • set rave_alerts_active_event to 1.
   • log ACTIVE token is found.
3. If no CLEAR token is found: (show alert)
   • set rave_alerts_display to 1.
   • log new rave rss event.

This seems like a decent replacement of the original code (see comments in #842), preserving its focus on the CLEAR token instead of the ACTIVE token. In the original code an alert was shown unless there was a CLEAR token in the title. The ACTIVE token was also searched for but that was not the condition that triggered an alert's display.

With these changes a [CLEAR] token should turn alerts off and its absence will 'turn on' an alert and log it. If there is an [ACTIVE] token there is an additional log entry and the setting rave_alerts_active_event = 1.

[github-actions[bot]]

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[AlanBCole]

While testing this again today, I noticed that the cache was never being emptied as expected. Apparently there is an issue with setting an expiration time in cache_set(). Basically, it doesn't do anything. (look here too -> https://api.drupal.org/api/drupal/includes%21cache.inc/function/cache_set/7.x#comment-58038)

Given the date of the comment linked to above, the rave_alerts module may have not been working 100% as expected for some years. Please do not merge this PR until I fix this as well.