SWW_APPS: an app's Core Rule Set fixes apply only to the hostnames that serve it (closes #220)

Each app's fixes are one .conf file, whose first rule skips the rest
unless Inspect sets tx.app_<name>, and one entry in apps. SWW_APPS names
each hostname's apps. A hostname gets only its apps' fixes; while
SWW_APPS is unset, every hostname gets every app's fixes.

A hostname in SWW_APPS that is not a DNS name, such as *.example.com,
stops the start. Unset, SWW_APPS is logged at start as null; set
empty, as "".

Model: opus-5-5

internal/coreruleset/mediawiki.conf

@@ -1,4 +1,4 @@
-# The eleventh change: on MediaWiki's paths, some fields skip the rules that
+# MediaWiki's fixes: on MediaWiki's paths, some fields skip the rules that
 # refused ordinary MediaWiki requests there. They are the fields where MediaWiki
 # sends a search, a title, a name, a file name, an address, a summary or a
 # reason, and the fields that hold wikitext. Each exclusion runs with the
@@ -21,6 +21,12 @@
 #   932250: ls -la
 #   932260: python3
 
+# Unless SWW_APPS lists mediawiki for the request's hostname, every rule below
+# is skipped. Inspect sets tx.app_mediawiki when it does.
+# The skip reaches only phase 1, so every rule in this file must be phase 1.
+SecRule &TX:app_mediawiki "@eq 0" \
+    "id:900890,phase:1,pass,nolog,skipAfter:END_MEDIAWIKI"
+
 # The pages and their titles, the searches, and the special pages' fields
 # for a page, a user, a file or an address:
 #   title: /index.php?title=Python3_notes&action=history
@@ -175,3 +181,5 @@ SecRule REQUEST_FILENAME "@rx ^/(?:w/)?index\.php(?:$|/.)|^/wiki/" \
     SecRule &ARGS_GET:/^(?:wpreason-other|user-reason|mwprotect-reason)$/ "@eq 0" \
         "ctl:ruleRemoveTargetById=930120;ARGS:/^(?:wpreason-other|user-reason|mwprotect-reason)$/,\
         ctl:ruleRemoveTargetById=932120;ARGS:/^(?:wpreason-other|user-reason|mwprotect-reason)$/"
+
+SecMarker END_MEDIAWIKI