DXCDT-252: Enable deletion of email provider (2/2)

[willvedd]

🔧 Changes

#653 highlighted that email provider cannot be deleted by this tool when setting the configuration as an empty object. Resource deletion is a first-class feature of this tool and an inability to delete is considered a bug. This PR implements that deletions functionality.

This PR is a draft only because it depends on #672 being released for some duration to offer adequate time to warn folks about this fix. Eventually, that warning will be removed and replaced with this PR.

📚 References

Original Github issue: #653 Part 1 PR: #672

🔬 Testing

Added test for empty-object configuration and subsequent deletion.

📝 Checklist

• [x] All new/changed/fixed functionality is covered by tests (or N/A)
• [x] I have added documentation for all new/changed functionality (or N/A)