Stringify task_instance.id when setting OTEL span attribute

[c-premus]

closes: #66052

Summary

_emit_task_span() in the execution API was setting the airflow.task_instance.id span attribute to the raw UUID object. The OTEL SDK only accepts str / bytes / int / float / bool attribute values (or homogeneous sequences), so it dropped the attribute and logged a warning per task state transition:

[warning  ] Invalid type UUID for attribute 'airflow.task_instance.id' value. Expected one of ['bool', 'str', 'bytes', 'int', 'float'] or a sequence of those types [opentelemetry.attributes] correlation_id=... loc=__init__.py:119 ti_id=...

The fix stringifies the UUID, matching the convention already used at the top of the same module (bind_contextvars(ti_id=str(task_instance_id))).

Root cause

Introduced in #63839 (merged 2026-03-24, "Introduce parent task spans and nest worker and trigger spans under them"). First shipped in 3.2.0; reproducible on 3.2.1 and main.

Reproduction

1. Run Airflow 3.2.x with native OTEL tracing enabled ([traces] otel_on = True and an OTLP endpoint).
2. Trigger any DAG.
3. docker logs <api-server> | grep "Invalid type UUID" — one warning per task state transition.

Impact

Cosmetic but noisy — the task itself runs fine, the span is still emitted with the other attributes (dag_id, task_id, run_id, try_number, map_index, state), only the TI UUID attribute is dropped. This prevents trace search by task instance ID in the trace backend.

Tests

Extended TestEmitTaskSpan.test_emit_task_span_sets_attributes to set a real UUID on the mock TI and assert the span attribute is present, equal to str(ti.id), and of type str.

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[boring-cyborg]

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[henry3260]

Thanks for your effort !

[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[github-actions]

Backport successfully created: v3-2-test

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Status	Branch	Result
✅	v3-2-test