Documentation request – forming a response to token

Hello, this may be out of the scope of issues for this project, but I've been all over trying to find a specification for how to form a token response that will cause AppAuth to close the browser window and complete the request making the payload available to my app.

This is a companion issue to this Stack Overflow question

In my particular case I have gone through the process up until the point where AppAuth browser window has been redirected to my server. It has presented the server with it's authCode and it's waiting for a response. My server has obtained a valid token and is ready to respond.

In looking around I have found documentation that states that AppAuth is compliant with RFC 8252, but the section in question 7.1 does not provide a specification for response structure.

What is the structure of the response that AppAuth is awaiting in this scenario?

It may be helpful to know that my scenario requires me to use a redirectUri that points to my token server. It's possible this is out of spec, and if so, I kindly request any suggestion for strategy to handle this scenario that is in spec. As you may know, auth is a bit of a nebulous topic for those of us who aren't intrenched in it, so it can be hard to penetrate from the outside. (As an explicit example, I am getting a token from Instagram and transforming it into a Firebase Auth token.)

Start with RFC 8252 §7.1 and the linked Stack Overflow question, then review the AppAuth-iOS redirect and token-exchange documentation mentioned by the issue. Document the expected response structure and clarify whether using a token server as the redirectUri is supported, including an in-spec strategy if it is not.