fix: valid username lowercase (#42172)

* fix: valid username lowercase

* test: add test in the validate for reject uppercase characters

* test: add test in the cypress for check on uppercase characters and reject it.

utils/validate.js

@@ -8,15 +8,20 @@ const usernameIsHttpStatusCode = {
   valid: false,
   error: 'is a reserved error code'
 };
+const usernameUpperCase = { valid: false, error: 'must be lowercase' };
 
 const isNumeric = num => !isNaN(num);
 const validCharsRE = /^[a-zA-Z0-9\-_+]*$/;
 const isHttpStatusCode = str =>
   isNumeric(str) && parseInt(str, 10) >= 100 && parseInt(str, 10) <= 599;
+const isUsernameLowercase = str => {
+  return str === str.toLowerCase();
+};
 const isValidUsername = str => {
   if (!validCharsRE.test(str)) return invalidCharError;
   if (str.length < 3) return usernameTooShort;
   if (isHttpStatusCode(str)) return usernameIsHttpStatusCode;
+  if (!isUsernameLowercase(str)) return usernameUpperCase;
   return validationSuccess;
 };
 
@@ -24,8 +29,10 @@ module.exports = {
   isNumeric,
   isHttpStatusCode,
   isValidUsername,
+  isUsernameLowercase,
   validationSuccess,
   usernameTooShort,
   usernameIsHttpStatusCode,
-  invalidCharError
+  invalidCharError,
+  usernameUpperCase
 };