Package main provides a minimal example server showing how to use the
authentication helpers from the common repository. It defines a simple
greeting handler and wires up the OAuth login and callback handlers from the
auth subpackage.
Environment variables:
GOOGLE_OAUTH_CLIENT_ID and GOOGLE_OAUTH_CLIENT_SECRET must be set with
credentials for a Google OAuth web client.
ADMIN_EMAILS optionally provides a comma separated list of admin
accounts allowed to log in.
PORT specifies the HTTP port for the server (default 8080).