Implement CborErrorResponseUnmarshaller with proper error type mapping

[muhammad-othman]

Description

• Implemented CborErrorResponseUnmarshaller.
• Implemented CborResponseUnmarshaller template.
• Generate CBOR exceptions protocol tests.

Motivation and Context

DOTNET-8163

Testing

• Added smithy-rpc-v2-cbor to CloudWatch and SecretsManager models protocols, generated the marshallers/unmarshallers, and executed some requests that caused exceptions using CBOR protocol.
• CBOR exceptions protocol tests.
• DRY_RUN-189b330f-eb5f-4133-ac78-d7348196911e.

Screenshots (if appropriate)

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

• My code follows the code style of this project
• My change requires a change to the documentation
• I have updated the documentation accordingly
• I have read the README document
• I have added tests to cover my changes
• All new and existing tests passed

License

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

[Copilot]

Pull Request Overview

This PR implements CBOR error response unmarshalling functionality to properly handle exception mapping in CBOR protocol responses. The changes enable AWS SDK to correctly parse and handle error responses when using the CBOR protocol, particularly addressing the difference between shape names and error codes in exception handling.

• Implements CborErrorResponseUnmarshaller with proper error parsing logic
• Updates exception matching in CborResponseUnmarshaller template to use shape original names
• Enables CBOR protocol exception tests by removing skip conditions

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
CborErrorResponseUnmarshaller.cs	Implements complete error response parsing logic for CBOR protocol
CborResponseUnmarshaller.tt	Updates exception matching to use ShapeOriginalName and handle code mapping
CborResponseUnmarshaller.cs	Generated code changes from template updates
ExceptionShape.cs	Adds ShapeOriginalName property to support CBOR exception identification
HttpProtocolTestGenerator.java	Enables CBOR exception protocol tests by removing skip condition

[Copilot]

Potential ArgumentOutOfRangeException if 'type' parameter is null or if the calculated substring indices are invalid. The method should validate the input parameter and handle edge cases where start >= end.

Suggested change

	{
	int start = type.IndexOf('#');
	start = start == -1 ? 0 : start + 1;
	int end = type.IndexOf(':', start);
	end = end == -1 ? type.Length : end;
	{
	if (string.IsNullOrEmpty(type))
	{
	return string.Empty;
	}
	int start = type.IndexOf('#');
	start = start == -1 ? 0 : start + 1;
	int end = type.IndexOf(':', start);
	end = end == -1 ? type.Length : end;
	// Validate indices
	if (start < 0 || end > type.Length || start >= end)
	{
	return type.Trim();
	}

[muhammad-othman]

I don't want to include these checks since this means we received a malformed response from the service.

[Copilot]

The CBOR map reading logic doesn't call reader.ReadEndMap() after the while loop, which could leave the reader in an inconsistent state. Consider adding reader.ReadEndMap() after the while loop.

Suggested change

	}
	}
	reader.ReadEndMap();

[muhammad-othman]

I skipped that ReadEndMap() since in the next step we re-read the response anyway to generate the typed exception and reset the reader anyway and didn’t want to add an unnecessary step.