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 and one entry in apps. They apply
only while Inspect has set the app's transaction variable, such as
tx.app_gitea. 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/mastodon.conf

@@ -1,4 +1,4 @@
-# The twelfth change: on Mastodon's paths, some fields skip the rules that
+# Mastodon's fixes: on Mastodon's paths, some fields skip the rules that
 # refused ordinary Mastodon requests there. They are the fields where Mastodon
 # sends a search, a name, a title, a file name, an address or free text. Each
 # exclusion runs with the request, before the rules it switches off, so this
@@ -17,6 +17,13 @@
 #   932250: ls -la
 #   932260: python3
 
+# Unless SWW_APPS lists mastodon for the request's hostname, every rule below is
+# skipped. Inspect sets tx.app_mastodon when it does.
+# The skip reaches only phase 1, so a rule of a later phase must check
+# tx.app_mastodon itself.
+SecRule &TX:app_mastodon "@eq 0" \
+    "id:900940,phase:1,pass,nolog,skipAfter:END_MASTODON"
+
 # The API's searches and names, in the query:
 #   q: /api/v2/search?q=python3, /api/v1/accounts/search?q=ls+-la
 #   acct: /api/v1/accounts/lookup?acct=python3
@@ -216,3 +223,5 @@ SecRule REQUEST_FILENAME "@rx ^/auth(?:/|$)" \
         "ctl:ruleRemoveTargetById=930120;ARGS:/^user\[email\]$/,\
         ctl:ruleRemoveTargetById=932120;ARGS:/^user\[email\]$/,\
         ctl:ruleRemoveTargetById=932260;ARGS:/^user\[email\]$/"
+
+SecMarker END_MASTODON