Add support to complete 3DS 2 transactions

[victor-paddle]

A new endpoint transactions/{token}/complete has been added to be able to complete a
3DS 2 transaction (https://docs.spreedly.com/reference/api/v1/transactions/). The SDK cannot reach that endpoint right now so a new method like the one below should be added to src/Transaction.php

    /**
     * Can be used to Completes a 3DS 2 transaction in the device fingerprint stage
     * See docs for more information.
     *
     * <code>
     *		// Completes a 3DS 2 transaction in the device fingerprint stage.
     *		Spreedly::transaction($transactionToken)->complete();
     * </code>
     *
     *
     * @return mixed
     *
     * @throws Exceptions\MissingTransactionTokenException
     */
    public function complete()
    {
        if (!$this->transactionToken) {
            throw new Exceptions\MissingTransactionTokenException();
        }

        return $this->client->post('v1/transactions/'.$this->transactionToken.'/complete.json');
    }

[tuurbo]

Thanks :)

[victor-paddle]

Thanks, is it possible to tag the release (ie: 2.3.3), please? 😄

[tuurbo]

Sorry about that, for some reason the tag wasn't pushed with the commit. Fixed now