Feature Request: [next-auth/react] Add ability to customize underlying

[william-will-angi]

Goals

1. Adding better client-side support for next-auth instances that are accessed cross-origin.

Non-Goals

1. This feature should not affect the ways that the underlying behave at all.

Background

We are exploring a setup where we have next-auth hosted on next-auth.app.com as a dedicated service, while a consuming app lives on frontend.app.com. The problem we are running into is that the fetch calls will not include the next-auth cookies necessary without adding a { credentials: 'include' } as an option to the request, so none of the client-side utilities work out of the box.

There are few places where this is discussed like here:
#1299 (comment)

Proposal

It seems like the simplest solution would be to add a prop to the SessionProvider component, that would allow you to customize this behavior, most likely updating the underlying fetch options.

I can probably put together a PR with what I am imagining.

I am willing to contribute to a discussion of this feature as well as creating the PR if the changes are not overly complex.

[willwill96]

I created a PR with the way I was thinking about the problem:
#12204