NuGet should indicate the credentials (or lack thereof) used when trying to access a private feed

[RanjiniM]

This is not a regression

When trying to restore from an authenticated feed whose credentials aren't specified in nuget.config a message "Please provide credentials for feed " is displayed

1. in White
2. Doesn't specify that the credentials should be specified in nuget.config in section
3. And an username prompt is emitted but the command continues to run without a chance for user to enter the credentials

Instead

1. Display the text in Red so the user knows that lack of credentials is the issue
2. Given more details on where to store these credentials. A doc link is much better
3. Better yet prompt for username, password

edit by @nkolev92

Additional ideas, leave breadcrumbs on higher verbosity about the authentication method used.
Nowadays, frequently some creds will be used, but they might be outdated/restricted etc.

We should also ensure that the http code is also communicated (40x)

[nkolev92]

Broadening the scope here.

In general this issue now refers to having some sort of breadcrumbs when doing authentication.

NuGet should indicate whether creds were used, how they were acquired etc.

We should cover all clients, and all NuGet operations.