Add route so new users can find their id_token
Add route so new users can find their id_token

Simplify the process for getting the id_token.  This still needs to read
the client id from the properties file.  All the javascript needs to be
moved into a separate file, and I'll add more styling.  This code mostly
comes from Google's [example
flow](https://developers.google.com/identity/sign-in/web/server-side-flow).
Once this is done I'll update the documentation accordingly.

PCNI/OpenHMIS,PCNI/OpenHMIS,PCNI/OpenHMIS,PCNI/OpenHMIS