Implemented users update button in frontend

src/Helpers/UsersHelper.cs

@@ -0,0 +1,44 @@
+using System.Globalization;
+using System.Text;
+using System.Text.RegularExpressions;
+namespace Berufsschule_HAM.Helpers;
+
+public static partial class UsersHelper
+{
+    public static string CreateUsername(string givenName, string surname)
+    {
+        if (string.IsNullOrWhiteSpace(givenName) || string.IsNullOrWhiteSpace(surname))
+            throw new ArgumentException("Given name and surname must not be empty.");
+
+        string combined = (surname + givenName).ToLowerInvariant();
+
+        // Normalize to decompose accents (e.g., é -> e +  ́)
+        string normalized = combined.Normalize(NormalizationForm.FormD);
+
+        // Remove diacritics
+        var sb = new StringBuilder();
+        foreach (var c in normalized)
+        {
+            var category = CharUnicodeInfo.GetUnicodeCategory(c);
+            if (category != UnicodeCategory.NonSpacingMark)
+                sb.Append(c);
+        }
+
+        string cleaned = sb.ToString();
+
+        // Replace German ligatures etc.
+        cleaned = cleaned
+            .Replace("ß", "ss")
+            .Replace("æ", "ae")
+            .Replace("œ", "oe")
+            .Replace("ø", "o");
+
+        // Remove everything not a-z
+        cleaned = AtoZ().Replace(cleaned, "");
+
+        return cleaned;
+    }
+
+    [GeneratedRegex("[^a-z]")]
+    private static partial Regex AtoZ();
+}