Add Werk 18920 FIX Check HTTP web service: Fix text searches

SUP-24931

Change-Id: I78172f6019d531a3bfc6b72442fd74cd0c6aaeb3

Author: andiumbreit

.werks/18920.md

@@ -0,0 +1,27 @@
+[//]: # (werk v2)
+# Check HTTP web service: Fix text searches
+
+key        | value
+---------- | ---
+date       | 2025-12-08T08:48:50+00:00
+version    | 2.3.0p42
+class      | fix
+edition    | cre
+component  | checks
+level      | 1
+compatible | yes
+
+In the _Check HTTP web service_ ruleset, when configuring _Search for strings > search for header > Regular expression > Return CRITICAL_ [sic] _if found, OK if not_, some bugs occured:
+
+**Wrong caption in ruleset**
+First of all: The caption should read _Return WARN if found, OK if not_, since _WARN_ is the fixed state that will be returned for all failing header/body string/regex searches.<br>
+Please note that this will change starting with Checkmk 2.4.0p18, see Werk #18921.
+
+**Inverted header regex search didn't work**
+The service yielded an _OK_ state most of the times, even if the regex _was_ found in the headers.<br>
+This happened because the search iterates over all headers and stopped on first expected result. If the first header didn't contain the regex, the engine was satisfied and didn't continue.
+
+**Wrong info on inverted header regex searches**
+Also the appended _(matched/not matched)_ info was swapped, leading to even more confusion.<br>
+Note: This info text will be enhanced a bit to be more meaningful, see also Werk #18921.
+