feat(signer): Notation-OCI-SHA384-ECDSA platform

[lpizzinidev]

Adds support for the Notation-OCI-SHA384-ECDSA signing profile platform.
Also, refactors the Platform class to an enum-like class to allow custom platforms (and prevent blocking users if added platforms are missing on the enum declaration).

Closes #28580.

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[kaizencc]

Thanks @lpizzinidev. It's a feat not a fix because you're adding in a new value that presumably didn't exist before.

[aws-cdk-automation]

The pull request linter has failed. See the aws-cdk-automation comment below for failure reasons. If you believe this pull request should receive an exemption, please comment and provide a justification.

A comment requesting an exemption should contain the text Exemption Request. Additionally, if clarification is needed add Clarification Request to a comment.

✅ Updated pull request passes all PRLinter validations. Dismissing previous PRLinter review.

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 2d7af03
• Result: SUCCEEDED
• Build Logs (available for 30 days)

Powered by github-codebuild-logs, available on the AWS Serverless Application Repository

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).