feat: Add OpenTelemetry instrumentation for aggregate populate

[yordis]

No description provided.

[cursor]

PR Summary

Introduces tracing for aggregate populate lifecycle.

• New Commanded.OpenTelemetry.AggregatePopulate attaches telemetry handlers for [:commanded, :aggregate, :populate, :start|:stop], creating internal span commanded.aggregate.populate with messaging/code semconv and Commanded attributes; sets commanded.event.count and final commanded.aggregate.version on stop
• Extends Commanded.OpenTelemetry.setup/1 with aggregate_populate option (can be :disabled) and wires to AggregatePopulate.setup/0
• Tests: added AggregatePopulateTest; updated test support with Factory.build_aggregate_populate_metadata/1 and OpenTelemetryCase cleanup for new events

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[coderabbitai]

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Walkthrough

Adds OpenTelemetry instrumentation for aggregate population: new Commanded.OpenTelemetry.AggregatePopulate module with telemetry handlers, wires setup and config option into Commanded.OpenTelemetry, and adds tests and factory/helper updates for aggregate populate events.

Changes

Cohort / File(s)	Summary
OpenTelemetry Core lib/commanded/opentelemetry.ex	Added Commanded.OpenTelemetry.AggregatePopulate alias; extended NimbleOptions schema with aggregate_populate option (accepts :disabled or list, default []); wired setup to call AggregatePopulate.setup() when enabled.
AggregatePopulate Instrumentation lib/commanded/opentelemetry/aggregate_populate.ex	New module implementing setup/0 and handle_telemetry_event/4; attaches handlers for [:commanded, :aggregate, :populate, :start] and [:commanded, :aggregate, :populate, :stop]; starts internal span on start and sets event_count/aggregate_version on stop.
Tests test/opentelemetry/aggregate_populate_test.exs	New test module verifying handler attachment, idempotency/fail-fast on double setup, span attributes (messaging, code, application, aggregate UUID/version, event count), and edge cases (zero/multiple events).
Test Helpers test/support/factory.ex, test/support/opentelemetry_case.ex	Added build_aggregate_populate_metadata/1 factory helper; extended OpenTelemetry case teardown to detach [:commanded, :aggregate, :populate, :start] and [:commanded, :aggregate, :populate, :stop] handlers.

Sequence Diagram(s)

sequenceDiagram
    participant Aggregate as Aggregate
    participant Telemetry as Telemetry
    participant Handler as AggregatePopulate<br/>(handler)
    participant OTel as OpenTelemetry<br/>Tracer

    Aggregate->>Telemetry: emit [:commanded, :aggregate, :populate, :start]
    Telemetry->>Handler: handle_telemetry_event/4 (start)
    Handler->>Handler: build attributes (messaging, code, commanded)
    Handler->>OTel: start_span("commanded.aggregate.populate")
    OTel-->>Handler: span_ref

    Aggregate->>Aggregate: populate aggregate (apply events)

    Aggregate->>Telemetry: emit [:commanded, :aggregate, :populate, :stop]
    Telemetry->>Handler: handle_telemetry_event/4 (stop)
    Handler->>Handler: set event_count & aggregate_version attrs
    Handler->>OTel: set_attributes(span_ref, attrs)
    Handler->>OTel: end_span(span_ref)
    OTel-->>Handler: span closed

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• feat: Add OpenTelemetry instrumentation for event handlers #41: Adds OpenTelemetry event-handler instrumentation and modifies lib/commanded/opentelemetry.ex similarly (related setup/schema changes).
• feat: implement OpenTelemetry instrumentation for application #46: Adds another OpenTelemetry instrumentation submodule and corresponding setup wiring in the same core module.

Poem

🐰 Hopping through telemetry trails so keen,

I trace each aggregate, seen and unseen.
Spans knitted with versions, counts in a row,
Tiny rabbit feet mark every flow.
Cheers for traces that help us grow! 🥕✨

🚥 Pre-merge checks | ✅ 1 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Description check	❓ Inconclusive	No pull request description was provided by the author, making it impossible to evaluate whether the description relates to the changeset.	Add a pull request description that explains the purpose and context of the aggregate populate instrumentation changes.

✅ Passed checks (1 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'feat: Add OpenTelemetry instrumentation for aggregate populate' directly and clearly describes the main change: adding OpenTelemetry instrumentation for aggregate populate events.

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✨ Finishing touches

• 📝 Generate docstrings

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[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.