iframes, cookies, Network Partition and how to create a session

[MattTLB]

Our application will be embedded in an iframe in another application, and the only way I have managed to get our oauth login to work is to use something similar to the solution here. This required me to change the cookies sameSite setting to none, whilst this works it is not ideal and got me thinking about other solutions.

Basically I sign in using a popup, but I am only signed in in the popup due to State Partitioning (or not in an iframe) but I now have an Access and Refresh token in a session, what if I use window.opener.postMessage in the popup and window.addEventListener('message', handleMessage); in the iframe to send my credentials back? This step was surprisingly easy!

Now I have my tokens but no idea how to get them into next-auth, does anyone have any ideas?