fix: allow only alphanumeric chars in username

web/pages/admin/config-federation.tsx

@@ -126,9 +126,7 @@ const ConfigFederation = () => {
     const usernameValue = value;
     const hasUsername = usernameValue !== '';
     if (hasUsername) {
-      if (usernameValue.includes('@')) {
-        const usernameWithoutServer = usernameValue.split('@').slice(0, -1).join('@');
-        if (usernameWithoutServer.length > 0 && isAlphanumeric(usernameWithoutServer)) {
+      if (isAlphanumeric(usernameValue)) {
         setIsUsernameValid(true);
       } else {
         setIsUsernameValid(false);
@@ -136,7 +134,6 @@ const ConfigFederation = () => {
     } else {
       setIsUsernameValid(false);
     }
-    }
   };
 
   const handleEnabledSwitchChange = (value: boolean) => {