Good day! I understand that you are looking to integrate a payment system into your existing Rails site. I have extensive knowledge of including external APIs into Rails and programming logic to handle specific tasks utilizing the APIs structure.
I have done so in not only Ruby, but even in strict programming languages (Java). Specific to Ruby, I have used the Plaid API to retrieve and display 3rd-party financial data. I not only have Rails experience, but many other client-side technologies as well (HTML, CSS, JavaScript, jQuery, AJAX, AngularJS).
I noticed you said you plan to host the payment platform through sharetribe, which claims to have functionality independent of developer necessity. I'm curious as to what you plan to do as far as integration with Sharetribe. I'd love to discuss further details about the project. Please feel free to contact me with any further details. I do not have much of a reputation here on freelancer as this would be my first job here, so I'm looking to get a start with a few project (hence the lower price).
Thank you!