feat: add authentik provider

[aoor9]

Hello,
this PR adds Authentik as provider

Steps

1. Set up your self-hosted Authentik instance
2. In the Admin interface, create your OAuth provider under Applications -> Providers and add your web app URL containing /auth/authentik inside Redirect URIs section (you can use localhost)
3. Retrieve Client ID and Client Secret and add them to .env file as NUXT_OAUTH_AUTHENTIK_CLIENT_ID and NUXT_OAUTH_AUTHENTIK_CLIENT_SECRET, along with your instance URL as NUXT_OAUTH_AUTHENTIK_DOMAIN

[pkg-pr-new]

Open in Stackblitz

pnpm add https://pkg.pr.new/atinux/nuxt-auth-utils@274

commit: fc55591