Implement authentication setup for the structures admin and individual applications.

[NavidMitchell]

We need the ability to configure authentication for the core structures system. This would be user that can authenticate to use the admin panel and add or modify structures using the cli.

Also we need the same ability to define authentication for each individual Application within in structures.

When defining authentication you should be able to pick from a list of predefined IDP's or manually configure one using OIDC or SAML.