How to setup nuxt for multi-tenancy with separate sessions, subdomains and single login page

[norotico]

I have the following multi-tenancy scenario:

• All users must login from app.example.com to create a "main" session.
• Logged in users must be redirected to app.example.com/choose-tenant
• When user navigates to one of his tenants, if his main session is active a new tenant-specific session is automatically created and he is redirected to his tenant's dashboard e.g. {dynamic-tenant-name}.example.com/dashboard

How would I go about setting up nuxt.config.js?

The use case is similar to #1153, but the suggested approach doesn't cover single page login and main session. The API endpoint should be api.example.com for authentication and api.{dynamic-tenant-name}.example.com for everything else.