Improve WAM error messages

[localden]

Right now, when WAM errors out, it throws an error that a developer might not understand the root cause of:

To reproduce this issue, I used WAM to access a resource without configuring the proper redirect URL.

Per @bgavrilMS:

You have to configure logging and set the PII flag to true there. But that's pretty hard to discover.

The error message from WAM actually told me that I was missing an app-specific redirect URL, but that is not clear from the error surface.

[bgavrilMS]

1. If PII flag is not set, let's add a message like To see this message, set the logging PII flag to true. See aka.ms/logging
2. For the redirect URI in particular, produce an error message telling the end user what they need to register.