func validatePassword(username: String, password:String) -> [String]{
        var errors:[String] = []

        if password.characters.count < 8 {
            errors.append("Password must have more than 8 characters.")
        }

        if (password.range(of:"[\\W]", options: .regularExpression) == nil){
            errors.append("Password must contain a special character.")
        }

        if (username == password){
            errors.append("Username and password MUST be different.")
        }

        return errors
    }

    validatePassword(username: "Richi", password: "Richi")
    /*
     * Array<String> 3 elements:
     - 0: "Password must have more than 8 characters."
     - 1: "Password must contain a special character."
     - 2: "Username and password MUST be different."
     */

    validatePassword(username: "Richi", password: "Ricardo$")
    /*
     * Array<String> 0 elements
     */