Server side authentication

[johanneskvamme]

Change from oidc-client to next-auth to allow for server side rendering.
This is motivated by a change coming to browsers which disallow iframe renewal of tokens, and as such users will be logged out often.
By using Next as a backend-for-frontend, Next can keep renew tokens and keep secrets, allowing for safe renewal of tokens through other flows than PKCE.

To-do before undraft:

• Fix types on pages/api/auth
• Fix types on useSession()'s returned user so that it can share a type with the one actually in use at pages/api/auth and not need (session.user as unknown as IAuthUser).profile. this to cast it every time it is needed.
• Renew access tokens on expiration

[vercel]

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[balazsorban44]

NextAuth.js maintainer her! Gi meg en pip hvis dere trenger hjelp med dette. 😉

Mye som har endret seg siden 3.1.0, vi har en v4 beta nå også (https://next-auth.js.org/getting-started/upgrade-v4)!

Innebygd TypeScript, bedre docs, enklere/mer logiske signaturer, osv.