Add regex section

README.md

@@ -40,3 +40,18 @@ In production it makes sense to run stechuhr with gunicorn:
 source env/bin/activate
 gunicorn stechuhr_server.server:app
 ```
+
+# Configuration
+
+## ID verification
+
+in `config.toml` you can add a list of regex patterns that stechuhr (*both on server and on client!*) uses to verify the Card IDs. These two patterns for example allow upper/lowercase hex strings with lengths either between 6 and 16 characters OR exactly 24 characters:
+
+```toml
+id_patterns = [
+    "^[A-Fa-f0-9]{24}$",
+    "^[A-Fa-f0-9]{6,16}$",
+]
+```
+
+If in doubt consider [testing your regexes here](https://regexplained.com/)
\ No newline at end of file

test.sh

 #! /bin/bash
 
-curl --header "Content-Type: application/json"  --request POST --data '{"location":"lerchenfeld", "entrance":"haupteingang", "direction":"in", "id":"543GFDHG"}' http://localhost:8000/
+curl --header "Content-Type: application/json"  --request POST --data '{"location":"lerchenfeld", "entrance":"haupteingang", "direction":"in", "id":"DEADBEEF42"}' http://localhost:8000/