Have the proxy redirect to HTTPS and/or refuse to proxy HTTP

### What should we add or change to make your life better?

If so configured through the configuration system
* have the proxy redirect to HTTPS, being able to add HSTS is then also relevant,
* or have the proxy refuse to proxy HTTP.

### Why is this important to you?

Although the authentication at the proxy works beautifully, these options would be required to fix security holes in old and/or simple apps which the proxy allows to expose:

* protect passwords and cookies for sites that use plain text passwords and the like
* it is just not very neat authentication over HTTP is properly refused but with error messages users shouldn't see
* it could well be desirable to disable HTTP altogether for an endpoint, which would be a good policy for API's to enforce at the proxy

This is what Azure AD gives me, with no way around this except writing the redirect manually and breaking the configurability:
```
Sign in
Sorry, but we’re having trouble signing you in.

AADSTS50011: The reply URL specified in the request does not match the reply URLs configured for the application.
```