aws-s3-deployment: Support CfnMapping (Fn::FindInMap) in deploy time values for Source.jsonData

[arvchahal]

Issue #30369

Closes #30369

Reason for this change

In large APIs with custom response templates—such as structured code error mappings—it's common to rely on CfnMapping to reduce template size and avoid CloudFormation's 1MB limit. Repeating static values throughout the template quickly causes size constraints.

By allowing Fn::FindInMap to be used in Source.jsonData, we enable developers to define the mapping once and reference it efficiently. This pattern helps optimize template size and maintainability for dynamic configuration values.

Solves issue

• Added support for Fn::FindInMap in deploy-time JSON data passed via Source.jsonData(...).

• Extended the renderData() logic to recognize Fn::FindInMap as a valid intrinsic.

• Added unit and integration tests to validate this support.
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Describe any new or updated permissions being added

N/A – no new permissions are introduced in this change.

Description of how you validated changes

• Added unit tests covering:
  - Valid use of Fn::FindInMap inside strings and as standalone values
  - Marker resolution for mixed Fn::Join inputs
  - Edge cases (e.g., invalid intrinsics, lazy resolution)
  • Added an integration test that synthesizes a stack using Fn::FindInMap within Source.jsonData and confirms successful
    binding.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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

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AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 11b8b5a
• Result: FAILED
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