Callback features

[maschnetwork]

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

Issue Link, if available

Description

• DurableContext.createCallback() API with configurable timeouts and custom SerDes support
• CallbackOperation handles checkpointing, suspension, and polling for completion
• Dedicated exceptions (CallbackTimeoutException, CallbackFailedException) for error handling
• Testing utilities extended with completeCallback(), failCallback(), and timeoutCallback() methods for LocalDurableTestRunner and CloudDurableTestRunner

Checklist

• I have filled out every section of the PR template
• I have thoroughly tested this change

Testing

Unit Tests

Have unit tests been written for these changes?

Yes

Integration Tests

Have integration tests been written for these changes?

Yes

Examples

Has a new example been added for the change? (if applicable)

Yes

[phipag]

Awesome work, and the cloud based tests also pass for me when deployed to my account. These comments are mostly cosmetic / minor. No major concerns about merging this.

[maschnetwork]

@zhongkechen and @phipag applied review comments. please take a look.

[phipag]

Code looks good, but the cloud integration tests are failing now. I think related to refactoring to EventType enum.

[ERROR] Errors: 
[ERROR]   CloudBasedIntegrationTest.testCallbackExample:252 » UnsupportedOperation Unsupported event type: ExecutionStarted
[ERROR]   CloudBasedIntegrationTest.testCallbackExampleWithFailure:287 » UnsupportedOperation Unsupported event type: ExecutionStarted
[ERROR]   CloudBasedIntegrationTest.testCallbackExampleWithTimeout:320 » UnsupportedOperation Unsupported event type: ExecutionStarted
[ERROR]   CloudBasedIntegrationTest.testCustomConfigExample:204 » Runtime Function invocation failed
[ERROR]   CloudBasedIntegrationTest.testErrorHandlingExample:233 » Runtime Function invocation failed
[ERROR]   CloudBasedIntegrationTest.testGenericTypesExample:168 » Runtime Function invocation failed
[ERROR]   CloudBasedIntegrationTest.testRetryExample:74 » Runtime Function invocation failed
[ERROR]   CloudBasedIntegrationTest.testRetryInProcessExample:94 » Runtime Function invocation failed
[ERROR]   CloudBasedIntegrationTest.testSimpleStepExample:61 » Runtime Function invocation failed
[ERROR]   CloudBasedIntegrationTest.testWaitAtLeastExample:134 » Runtime Function invocation failed
[ERROR]   CloudBasedIntegrationTest.testWaitAtLeastInProcessExample:151 » Runtime Function invocation failed
[ERROR]   CloudBasedIntegrationTest.testWaitExample:116 » Runtime Function invocation failed
[INFO] 
[ERROR] Tests run: 12, Failures: 0, Errors: 12, Skipped: 0

[maschnetwork]

Fixed CloudIntegration Tests. Was missing some cases in the new switch when moving from if/else approach

Discussed with Philipp offline and fixed remaining Integration tests.