pass the full user object to findUsing callback

[joelclermont]

NOTE: this is a breaking change. If anyone is passing a custom callback for findUsing to authenticate, it will need to be updated.

We are trying to support a hybrid login for an existing Laravel application where a subset of users (on a certain domain) use WorkOS, and the rest use the local login logic. We needed to customize findUsing to look up a user based on email, not just the workos_id, but we were unable to do it since the callback was only being passed the id.

createUsing and updateUsing deal with full user objects, so this also adds symmetry to the findUsing method.

I'd normally add/update tests with a PR, but I don't see any tests. I'd be happy to build out test coverage, but that would be a separate PR.

[ckeller03]

Thanks @joelclermont. I like the consistency with this change so that all the methods use the full user object, makes a lot of sense!