Auth: Integration of local IDP

[thomasdanan]

First iteration of Authentication feature: Ability to provision users/passwords using embedded IDP

Spec:
Design:

• Using Salt, generate self-signed certificates needed for Dex deployment (Setup Dex to run over TLS using self-signed certs #2008)
• Deploy Dex in MetalK8s from the official Dex Charts while making use of
• the generated certificates above (Deploy Dex in MetalK8s from the Helm charts #2007)
• Configure Kubernetes API server flags to use Dex (Setup the Dex-to-Kubernetes API server integration  #2010)
• Expose Dex on the control plane using Ingress (Expose Dex on the control-plane ingress controller #2011)
• Implement MetalK8s UI integration with Dex (Configure the UI to require authentication through Dex #2015)
• Theme the Dex GUI to match MetalK8s UI specs (Brand the Dex GUI to match the MetalK8s UI specs #2016)