Fix NPE in TryExecutor when retry policy omits optional fields

[mcruzdev]

The spec defines backoff, limit, and delay as optional in a retry policy, but the runtime assumed all three were always present, causing NullPointerException when any was omitted.

• Default to constant backoff when backoff is not specified
• Default to unlimited retries when limit is not specified
• Default to zero delay when delay is not specified

Closes #1517

[Copilot]

Pull request overview

This PR addresses runtime NullPointerException failures when a RetryPolicy omits optional fields (as allowed by the spec) by adding defaulting/guard logic in the retry executor path and adding regression tests for common omission scenarios.

Changes:

• Default retry backoff to constant backoff when retryPolicy.backoff is omitted.
• Default retry limit to a max when retryPolicy.limit / limit.attempt is omitted.
• Default retry delay to Duration.ZERO when retryPolicy.delay is omitted.
• Add fluent DSL tests covering retry behavior when backoff, limit, or delay are omitted.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
impl/core/src/main/java/io/serverlessworkflow/impl/executors/TryExecutor.java	Adds resolveMaxAttempts() and defaults missing backoff to constant backoff.
impl/core/src/main/java/io/serverlessworkflow/impl/executors/retry/AbstractRetryIntervalFunction.java	Defaults missing delay to zero duration via a constant resolver.
experimental/test/src/test/java/io/serverlessworkflow/fluent/test/FuncTryCatchTest.java	Adds regression tests for retry policies missing backoff, limit, or delay.

Comments suppressed due to low confidence (1)

impl/core/src/main/java/io/serverlessworkflow/impl/executors/retry/AbstractRetryIntervalFunction.java:42

• The constructor still dereferences jitter.getFrom() / jitter.getTo() without guarding against them being null. The fluent builder allows setting only one of these, so this path can still throw a NullPointerException even with the top-level jitter != null check. Suggest treating missing from/to as no jitter (Duration.ZERO).

    if (jitter != null) {
      minJitteringResolver = Optional.of(WorkflowUtils.fromTimeoutAfter(appl, jitter.getFrom()));
      maxJitteringResolver = Optional.of(WorkflowUtils.fromTimeoutAfter(appl, jitter.getTo()));

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[fjtirado]

Lets move this one to WorkflowUtils and reference both in WorkflowUtils and here.

[fjtirado]

Suggested change

	if (limit == null || limit.getAttempt() == null) {
	return 0;
	}
	return limit.getAttempt().getCount();
	return limit != null && limit.getAttempt() != null ? limit.getAttempt().getCount() : 0;

[fjtirado]

Just usual picky comments ;)