Add support for optional authentication

[navalchand]

No description provided.

[vercel]

@navalchand is attempting to deploy a commit to the LangChain Team on Vercel.

A member of the Team first needs to authorize it.

[bracesproul]

Thanks for putting this up! I have a couple requests though:

1. Instead of passing in just the anonymous user ID and none of the other User object fields, we should just have an AnonymousUser object which is exported & used in place of the one returned from supabase that has all the User fields populated (with dummy field ofc)
2. This anonymous user object should be passed as props at the top level so that none of the sub components need to be updated
3. The isAnonymousUser util should instead check for a new env var NEXT_PUBLIC_IS_AUTH_DISABLED, this way if someone wants to use auth but forgets to set the proper env vars they'll be alerted.

If you could make those changes that would be great. Just dismiss this review and re-request my review again once done! Thanks again.