Enhancement: Add Function to Check Voucher Validity

[hendurhance]

Description:

Issue: #42

Fix Commit: [feat-valid-vouchers 1f2ea43]

I've created a pull request to address the issue raised by @Temian1 regarding checking the validity of a voucher. The proposed change introduces a new function called isValid() that allows users to check whether a voucher is still valid or has been used.

Code Changes:

/**
 * @param string $code
 * @return bool
 */
public function isValid(string $code): bool
{
    try {
        $this->check($code);
    } catch (VoucherIsInvalid $exception) {
        return false;
    } catch (VoucherExpired $exception) {
        return false;
    }

    return true;
}

This function will return true if the voucher is valid and false if it's invalid or has expired.

[mechelon]

Next to the code change, could you add a sentence to the README so the new feature is documented? Thanks!

Nice addition. 👍

[hendurhance]

Thank you for your feedback! I've made the requested changes, introducing two distinct methods, isValidCode and isValidVoucher, to enhance clarity and consistency. You can now easily validate voucher codes or voucher models without any ambiguity.

Additionally, I've updated the README to reflect these changes. Now, you can refer to the documentation for clear usage examples:

Vouchers::isValidCode('ABCD-EFGH'); // true or false
Vouchers::isValidVoucher($voucher); // true or false