Improve CloudEvent defaults for emitted events (#1554)

[anuragpaul602-netizen]

What & why

Fixes #1554.

Emitted CloudEvents (emit.event.with) were under-specified relative to the spec, which requires id, source, and type:

Field	Before	After
id	auto UUID — good	unchanged
type	throws if missing — correct	unchanged
source	falls back to reference-impl — no traceability	derived from workflow identity / configurable
time	omitted entirely	defaults to OffsetDateTime.now()

How

• source — when an emit declares no source, derive it from the emitting workflow's identity, namespace:name:version, via a new CloudEventUtils.source(WorkflowDefinitionId). EmitExecutor.buildCloudEvent already has the WorkflowContext, so no new plumbing is needed. The no-arg static fallback changes from reference-impl to urn:serverlessworkflow:sdk-java.
• time — in EmitExecutor, when the timeFilter is empty, set withTime(OffsetDateTime.now()) instead of omitting the attribute. Explicit literal/expression time is untouched.
• Application-level default source — new WorkflowApplication.Builder#withDefaultEventSource(URI|String) lets an application set one source for all emitted events.
• Resolution order (highest wins): explicit per-emit source → application-level default → workflow-identity-derived → static fallback.

Validation

EventProperties is deliberately left without @NotNull/@NotBlank annotations: it is shared between the emit and filter contexts, where required-ness differs, so annotating it would break filter use. With id, source, and time now all defaulted, type remains the only required emit attribute and EmitExecutor already throws when it is missing — runtime enforcement remains the correct approach.

Compatibility note

Changing the default source from reference-impl is a behavioral change; downstream consumers that filtered or asserted on source == "reference-impl" will need to update. This seems acceptable pre-1.0 but is called out here for release notes.

Testing

EmitCloudEventDefaultsTest (new) registers a capturing EventPublisher and asserts:

• an emit with no source gets source == namespace:name:version and a time close to now;
• an application-level default source overrides the identity-derived one;
• an explicit per-emit source overrides the application default.

Full impl/test + impl/lifecycleevent suites pass (239 tests), confirming no regression in lifecycle-event or correlation behavior.

Downstream

Quarkus Flow tracks the DSL-ergonomics side in quarkiverse/quarkus-flow#776.

🤖 Generated with Claude Code

[fjtirado]

This is a duplicate of #1556