[Logging] Add logging to DownstreamApi

[jennyf19]

Add more logging to DownstreamAPI, as currently it's difficult to debug issues.

After updating this sample, find places to add more logging in DownstreamAPI, especially in the case of misconfiguration and failures...for example not having the scopes in a collection.

[westin-m]

leave the test app for an e2e
provoke different errors

• add a space in BaseUrl
• use wrong scopes(token acquisition)
• spelling errors for the API

See what errors you get, add logging for that area and move to the next error.
Push up the additional logging and do a PR but remove the sample from the project first

[jennyf19]

@westin-m Let's make sure we have a log message here maybe as part of an else, to say that the call is unauthenticated. This will help us/partners with debugging. Could be an info/debug level log message.