Parent provided family loan to help with down payment of house. What is the best way to document the family loan and how does this get reported for taxes?

Earlier this year, I purchased a house and, though I had the funds, my parent insisted to support financially. We have a very good relationship and they expect no payment or strings attached in return (truly). However, I want to treat it as a family loan so that I don’t have to pay taxes on that amount since it’s over the $15,000 tax free gift amount (I live in the US).

I’ve heard a way to document the family loan is via a promissory note. Is that the best way?
Are there recommendations for a good promissory note template?
What terms do I need to be aware of setting with the note and what kind of interest needs to be paid back with it?

How should this transaction get reported on my taxes? I live in the US.