Add-on Plugin that triggers after user login

I need a small plugin script for XenForo to be developed.

This simple script is triggered after a user logs in to XenForo. The script then pulls the Ontraport Contact ID from the user's custom fields, it then makes an API call to Ontraport to update a certain field for that user.

1) the Xenforo user does not have an Contact ID, or
2) a matching record cannot be found in Ontraport,
then an email can be sent to a certain address.

FYI: All users should have a Contact ID on their account, as all users are created manually in XenForo (The checks above are just in case of an input error).

I have the API code for Ontraport. So I all I need is a small plugin for Xenforo.

Experience with the Ontraport API is great... but optional as it's a simple REST API call.

I look forward to working with a talented developer as this is the first step of a more robust integration between Ontraport and XenForo.