message: Reuse functions in UsernameValidation
diff: @@ -8,6 +8,9 @@ export class UsernameValidation {
  }
  public static isValid = (username: string): boolean => {
  - return username && username.length >= 3 && new RegExp(/^[0-9a-z_]+$/i).test(username)
  + return (
  + UsernameValidation.hasValidLength(username) &&
  + UsernameValidation.hasValidCharacters(username)
  + )
  }
  }
  