This copies the login command from the previous holos cli. Wire
dependency injection and all the rest of the unnecessary stuff from
kubelogin are removed, streamlined down into a single function that
takes a few oidc related parameters.
This will need to be extracted out into an infrastructure service so
multiple other command line tools can easily re-use it and get the ID
token into the x-oidc-id-token header.
Remove the server.Config struct, not needed. Remove the app struct and
move the configuration to the main holos.Config.ServerConfig.
Add flags specific to server configuration.
With this patch logging is simplified. Subcommands have a handle on the
top level holos.Config and can get a fully configured logger from
cfg.Logger() after flag parsing happens.
