archwiki: Do page view caching[1] with nginx for improved performance

We have used MediaWiki's file cache[2] until now, but recently the wiki has been hammered with requests from some stupid Chinese bots/crawlers.

Caching at the web server level is faster as we avoid the PHP overhead and it seems to make a difference (performance wise), especially when the bots/crawlers are hitting us.

This is usual done with Varnish[3], but I went with a simple Python service (30 LOC) for handling the PURGE requests as that is much simpler thn adding Varnish to our stack.

[1] https://www.mediawiki.org/w/index.php?title=Manual:Performance_tuning&oldid=6670283#Page_view_caching
[2] https://www.mediawiki.org/wiki/Manual:File_cache
[3] https://www.mediawiki.org/wiki/Manual:Varnish_caching

Fix #315 (closed)

roles/archwiki/tasks/main.yml

@@ -107,8 +107,6 @@
     - archwiki-runjobs.service
     - archwiki-runjobs-wait.service
     - archwiki-runjobs.timer
-    - archwiki-prune-cache.service
-    - archwiki-prune-cache.timer
     - archwiki-question-updater.service
     - archwiki-question-updater.timer
     - nginx-cache-purge.service
@@ -121,7 +119,6 @@
     daemon_reload: true
   with_items:
     - archwiki-runjobs.timer
-    - archwiki-prune-cache.timer
     - archwiki-runjobs-wait.service
     - archwiki-question-updater.timer
     - nginx-cache-purge.service