(#3242) Attempt default credentials for sources

[corbob]

Description Of Changes

Attempt to use the default credentials for the first attempt at a source.

Important note of behaviour change: If we are not able to authenticate with a source, we now prompt 3 times instead of 4, and the first one is prefaced with an Invalid credentials specified warning.

Motivation and Context

When attempting a query to a source that requires credentials, we were always prompting for credentials. This prevents attempting the default credentials unless entering an empty password. We should attempt initially with the default credentials, and only prompt if it's a retry for credentials.

Testing

1. Ran Test Kitchen test suites. All tests behaved as expected.
2. Ran some manual tests against an authenticated source without username/password. Confirmed it still prompted for credentials.
3. Ran some manual tests against a Windows authenticated source without username/password. Confirmed that it worked correctly.

Automated test suite:

1. Installed the (signed) choco build from Team City
2. Ran new ./Invoke-AuthedTests.ps1 script
3. Confirmed that all test failures reported were explainable.

Some output screenshots of the authenticated tests without username/password provided:

• Chocolatey CLI 2.1.0

- Chocolatey CLI debug build

Operating Systems Testing

• Windows Server 2016
• Windows Server 2019

Change Types Made

• Bug fix (non-breaking change).
• Feature / Enhancement (non-breaking change).
• Breaking change (fix or feature that could cause existing functionality to change).
• Documentation changes.
• PowerShell code changes.

Change Checklist

• Requires a change to the documentation.
• Documentation has been updated.
• Tests to cover my changes, have been added.
• All new and existing tests passed?
• PowerShell code changes: PowerShell v2 compatibility checked?

Related Issue

Fixes #3242

[vexx32]

This appears to work as described in a test environment. Nice work, Cory! Thanks for sorting this out! 💖