When sending payment through stellar.org, the txn hash should be given to user

[VincentTide]

If the transaction hash was given to the user upon sending a payment, the user would have something to give the merchant in case of issues arising.

The merchant can then do a quick trace using the provided transaction hash to ensure that

1. They sent it to the right address and destination tag.
2. Easier troubleshooting of any issues on the merchants end.