Add CompletableFuture version of suspend, resume and cancel

[fjtirado]

See quarkiverse/quarkus-flow#864 (comment)

[Copilot]

🟡 Changes recommended

The cancel-path now cancels dependent futures before emitting the workflow-cancelled lifecycle event, which can change observable event ordering and undermine the sequencing guarantees this PR aims to enable.

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Pull request overview

Adds CompletableFuture-based variants of workflow control operations (suspend/resume/cancel) so callers can compose/sequence these operations and (in some implementations) wait for lifecycle-event processing to complete.

Changes:

• Added suspendFuture(), resumeFuture(), and cancelFuture() to WorkflowInstance as default methods.
• Refactored WorkflowMutableInstance suspend/resume/cancel to share internal logic and added CompletableFuture<Boolean> variants that chain on lifecycle event publication.

File summaries

File	Description
impl/core/src/main/java/io/serverlessworkflow/impl/WorkflowMutableInstance.java	Adds future-returning control operations and refactors existing ones to share internal state-change logic and (for futures) await listener publication.
impl/core/src/main/java/io/serverlessworkflow/impl/WorkflowInstance.java	Extends the public instance API with default future-returning suspend/resume/cancel methods for compatibility.

Review details

Suppressed comments (1)

impl/core/src/main/java/io/serverlessworkflow/impl/WorkflowMutableInstance.java:253

• New suspendFuture()/resumeFuture()/cancelFuture() behavior is not covered by tests. Given existing lifecycle-event tests cover suspend/resume/cancel, it would be valuable to add coverage that the returned CompletableFuture completes only after the corresponding lifecycle listeners/events have finished processing (the main motivation for introducing these APIs).

  @Override
  public CompletableFuture<Boolean> suspendFuture() {
    return _suspend()
        ? publishEvent(
                workflowContext,
                l -> l.onWorkflowSuspended(new WorkflowSuspendedEvent(workflowContext)))
            .thenApply(__ -> true)
        : CompletableFuture.completedFuture(false);
  }

• Files reviewed: 2/2 changed files
• Comments generated: 3
• Review effort level: Lite

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