Update a payment with check pdf using Webservice or REST API

Summary:

Hi, We are planning to de-scope a legacy application that holds our checks. And thus, we are planning to move these checks to their corresponding Payments page on Oracle.

Is it possible for me to utilize a Webservice or REST API that I can build into an OIC Integration - that can read the file from an FTP Folder and attaches that PDF file to the Payment.

Can you please direct me to a webservice or REST API that can do the above?

Content (required):

The plan is to use an OIC integration that reads a file from FTP and attaches that file to the Payment using a Payment ID or Check ID as an input parameter.