Propagate errors to AppSync

[sobolk]

Problem

When errors are thrown in Lambda they are not propagated to upstream AppSync instance.

This is due to asynchronous dispatch from AppSync to Lambda.

Changes

The changes in this PR are to catch and forward as many errors as possible.

1. Add section in conversation turn executor that attempts to send error back to AppSync in a form of mutation (this is best effort as communication to AppSync might be impaired as well).
2. Refactor conversation turn executor's initialization logic to make it lazy. So that validation errors from that phase are captured and sent to AppSync as well.
3. Adjusted tests and e2e mock schemas to accommodate extra errors field.

Validation

1. Added tests (unit and e2e)
2. Manual validation with upstream.

Screenshot from e2e testing with AppSync using snapshot release:

Checklist

• If this PR includes a functional change to the runtime behavior of the code, I have added or updated automated test coverage for this change.
• If this PR requires a change to the Project Architecture README, I have included that update in this PR.
• If this PR requires a docs update, I have linked to that docs PR above.
• If this PR modifies E2E tests, makes changes to resource provisioning, or makes SDK calls, I have run the PR checks with the run-e2e label set.

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

[changeset-bot]

🦋 Changeset detected

Latest commit: 4a7fd00

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@aws-amplify/ai-constructs	Minor
@aws-amplify/backend-ai	Patch

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