chore(stepfunctions): added an ICatchable interface for step function states

[jasdeepbhalla]

Issue #35608

Closes #35608

Reason for this change

The Step Functions module currently lacks a type-safe way to represent states that support error handling via .addCatch().
When building reusable Step Function constructs or patterns, developers often need to specify that a state supports catching errors — similar to how INextable and IChainable express chaining behavior.

Adding an ICatchable interface improves type safety, clarity, and discoverability for these use cases.

Description of changes

• Added a new ICatchable interface to aws-stepfunctions/lib/types.ts.

• Defined the interface as:

  export interface ICatchable {
    addCatch(handler: IChainable, props?: CatchProps): INextable;
  }
  

• No breaking changes — this is a purely additive enhancement.

• Enables reusable constructs to define parameters as IChainable & ICatchable for stronger type guarantees.

Describe any new or updated permissions being added

N/A – No new IAM permissions are introduced by this change.

Description of how you validated changes

• Verified compilation and lint checks.

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

[aws-cdk-automation]

(This review is outdated)

[wimlewis-amazon]

This looks good to me.

We could consider declaring some of the actual catchable classes as implementing ICatchable, to make it explicit that the signatures match. The INextable interface does that (e.g., class DistributedMap extends MapBase implements INextable etc.).

[jasdeepbhalla]

Make sense will update the code, Thanks :)

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

[jasdeepbhalla]

@wimlewis-amazon Can you review the changes? Do they looks good?

[jasdeepbhalla]

@wimlewis-amazon @pahud This PR is ready for review!

[wimlewis-amazon]

These changes look good to me! (The re-typing to this is a nice improvement as well IMHO).

(I'm not associated with the CDK project, so I can't officially approve the PR, but 👍 anyway)

[aws-cdk-automation]

This PR cannot be merged because it has conflicts. Please resolve them. The PR will be considered stale and closed if it remains in an unmergeable state.

[aws-cdk-automation]

This PR cannot be merged because it has conflicts. Please resolve them. The PR will be considered stale and closed if it remains in an unmergeable state.