Extend status-page web application to allow sign-in with github IdP

[fkr]

The status-page web application needs to allow a sign-in with an IdP so that the policy layer can evaluate wether a user is allowed to access certain resources.

Definition of Ready:

• Create foundation for status page web-app #365
• Create example caddy deployment to serve as the policy layer #367
• Discuss status API server readiness for user authentication #627
• Create UI design for status page login feature #628

Definition of Done:

• As a user of the status-page web application I can click on a button and sign in with github

[berendt]

Why GitHub? At least when I use this as a CSP I want to use my internal IdP (Keycloak at the moment). If a customer needs a login via IdP, this will probably also be the internal IdP and not one of the public IdPs like GitHub.

[fkr]

Because this is about having a quick result for evaluating the flow between the frontend application, the policy layer and the backend. Once we know that this flow works nicely we’ll make sure to document on how to hookup other IdPs.

[joshuai96]

@berendt as it currently stands, dex will be the central component regarding AuthN. dex uses conectors, which configure upstream IdPs. So switching between GitHub and LDAP for example, is just a matter of configuration.