Payment verification

It seems that we don't record user transaction for now, and we are likely to use google analytics to have an idea of what happened.

In order to make my future implementation of bitcoin, and to provide a way to make sure that a payment is not already processed I created a new schema. We can choose to delete it after a transaction is made or keep it for record, but it can protect from a malicious user updating his result page and therefore obtaining more gem(after payment) .