Fix Invoke-AWSSSOLogin failure when default profile is configured for SSO login

[sankettangade]

Description

Fix Initialize-AWSSSOConfiguration -ProfileName default so it writes the profile under [default] section header in ~/.aws/config instead of the [profile default]. Every profile uses [profile <name>] except the default profile, which must be just [default].

Both AWS CLI and the existing AWSLoginProfileMethods in this project (used by Invoke-AWSLogin) already handle this edge case correctly.

Changes:

• SSOProfileMethods.RegisterSsoProfileAndSession now writes [default] when the profile name is default
• Cleanup: corrected error message at SSOCmdlets.cs:122 that referenced {ProfileName} in a branch where it was always null.

Motivation and Context

Testing

Tested locally on Windows and on a fresh EC2 Windows instance:

1. Original repro: Initialize-AWSSSOConfiguration -ProfileName default followed by Invoke-AWSSSOLogin (no args). Verified the section is written as bare [default] and the no-args login succeeds.
2. End-to-end credential resolution: Confirmed Get-S3Bucket works against the SSO-configured default profile.
3. Pre-existing keys preservation: Pre-populated [default] with region and other keys; confirmed unrelated keys survive after running the init cmdlet (matches aws configure sso behavior).
4. Non-default profile regression: -ProfileName myprofile still produces [profile myprofile] as before.

Dry-run

• Dry-run ID: b4119f1b-f35a-4ac5-86ee-417e7173ad38
• Status:
  • Pending
  • Completed successfully
  • Failed
• Failed bypass reason:

Breaking Changes Assessment

No Breaking Changes

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Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

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License

• I confirm that this pull request can be released under the Apache 2 license