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/wordpress.conf

@@ -1,10 +1,17 @@
-# The ninth change: on WordPress's paths, some fields skip the rules that refused
+# WordPress's fixes: on WordPress's paths, some fields skip the rules that refused
 # ordinary WordPress requests there. Each exclusion runs with the request, before
 # the rules it switches off, so this file is loaded before the Core Rule Set's
 # rules. Each comment names a request the rule refused. An exclusion on a field
 # of a body applies only when the query has no parameter of that name, so it
 # matters only while SWW_WAF_BODY_LIMIT is set.
 
+# Unless SWW_APPS lists wordpress for the request's hostname, every rule below is
+# skipped. Inspect sets tx.app_wordpress when it does.
+# The skip reaches only phase 1, so a rule of a later phase must check
+# tx.app_wordpress itself.
+SecRule &TX:app_wordpress "@eq 0" \
+    "id:900690,phase:1,pass,nolog,skipAfter:END_WORDPRESS"
+
 # WordPress takes a call to its REST API at any of four addresses:
 #   /wp-json/wp/v2/posts/1
 #   /index.php/wp-json/wp/v2/posts/1
@@ -195,3 +202,5 @@ SecRule REQUEST_FILENAME "@rx ^/(?:(?:index\.php/)?page/[0-9]+/?|index\.php)?$"
 # so skips 932340 there.
 SecRule REQUEST_FILENAME "@streq /wp-admin/upload.php" \
     "id:900711,phase:1,pass,nolog,ctl:ruleRemoveTargetById=932340;ARGS:_wp_http_referer"
+
+SecMarker END_WORDPRESS