Update documentation, optimise regex_replace, add tests

docs/customize/Tokenizers.md

@@ -67,7 +67,12 @@ Here is an example configuration file:
 
 ``` yaml
 query-preprocessing:
-    - normalize
+    - step: regex_replace
+    replacements:
+        - pattern: https?://[^\s]* # Filter URLs starting with http or https
+          replace: ''
+    - step: normalize
+
 normalization:
     - ":: lower ()"
     - "ß > 'ss'" # German szet is unambiguously equal to double ss
@@ -88,8 +93,8 @@ token-analysis:
             replacements: ['ä', 'ae']
 ```
 
-The configuration file contains four sections:
-`normalization`, `transliteration`, `sanitizers` and `token-analysis`.
+The configuration file contains five sections:
+`query-preprocessing`, `normalization`, `transliteration`, `sanitizers` and `token-analysis`.
 
 #### Query preprocessing
 
@@ -106,6 +111,17 @@ The following is a list of preprocessors that are shipped with Nominatim.
         heading_level: 6
         docstring_section_style: spacy
 
+::: nominatim_api.query_preprocessing.regex_replace
+    options:
+        members: False
+        heading_level: 6
+        docstring_section_style: spacy
+    description: 
+        This option runs any given regex pattern on the input and replaces values accordingly
+    replacements:
+        - pattern: regex pattern
+          replace: string to replace with
+
 
 #### Normalization and Transliteration