feat(validation): Add Middy.js middleware for JSON Schema validation

[VatsalGoel3]

Summary

This PR introduces a validationMiddleware function for Middy.js, enabling JSON Schema validation for both inbound (event) and outbound (response) payloads in AWS Lambda functions. This middleware leverages the existing validate function to ensure input and output payloads adhere to defined schemas, improving type safety and error handling in serverless applications.

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Changes

• Implemented validationMiddleware.ts, which:
  • Supports inbound validation (before hook) to validate event payloads.
  • Supports outbound validation (after hook) to validate Lambda responses.
  • Allows optional envelope extraction, custom formats, external schema references, and custom AJV instances.
  • Returns an empty object if neither inboundSchema nor outboundSchema is provided.
• Updated index.ts to export the validationMiddleware.
• Added middleware.test.ts to ensure 100% test coverage, verifying:
  • ✅ Successful inbound & outbound validation.
  • ✅ Handling of validation failures (both input and output).
  • ✅ No-op behavior when no schemas are provided.
  • ✅ Compliance with repository best practices

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Issue number closes #3609

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Checklist

• Follows contribution guidelines
• Does not duplicate an existing PR
• Passes all unit tests and meets 100% coverage threshold
• Uses Prepare/Act/Assess format in tests
• Ensures strict typing (no explicit any)
• Follows repository coding and linting standards

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[dreamorosi]

Hi @VatsalGoel3 could you please rebase the branch with the current main so it removes the conflicts?

[dreamorosi]

Thank you for the PR, I left some minor comments

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[VatsalGoel3]

@dreamorosi, I have made the requested changes and updated the test file as well, let me know if any more improvements are needed

[dreamorosi]

Thank you for this PR @VatsalGoel3!

We won't be releasing this module in the next release (this Friday) because we already have another feature coming up and we won't have time to review the documentation but I expect to include it in the next one (in ~2.5 weeks).

Over the next few days I'll be adding a few more issues to the backlog, in addition to the ones that are already marked as help-wanted (admittedly not many at the minute).

So keep an eye on the repo if you're interested in working on more!

[github-actions]

@aws-powertools/lambda-typescript No related issues found. Please ensure 'pending-release' label is applied before releasing.

[VatsalGoel3]

@dreamorosi Thank you for the update, I would like to contribute more to the project or any relevant projects if possible, also is there any better way I can keep in contact with you, for better workflow. I'll keep a lookout for the coming issues.