Payment link

I asked this question and it was answered. I can not find it. So unfortunately I'm asking again.

What is the endpoint for making an emailable payment link?

From memory: I create the invoice in QBO (from an API call), I get the ID back from the call, I use that ID, in the endpoint I'm asking about, and create an emailable link from a 3rd party software. 

From that link, my customer can pay that specific invoice, just as if I had emailed them from my QBO instance.