Airflowctl dags trigger fails with extra_forbidden against Airflow < 3.2.0

### Airflow CTL Version Latest stable version ### Airflow CTL Command airflowctl dags trigger example_simplest_dag --dag-run-id <run_id> --env production ### Keyring Backend / Version Keyring Backend/Headless ### Auth Type Token ### What is the current behaviour? `airflowctl dags trigger` fails against any Airflow deployment running a version earlier than 3.2.0, with: {'type': 'extra_forbidden', 'loc': ['body', 'partition_key'], 'msg': 'Extra inputs are not permitted', 'input': None} Root cause: `DagOperations.trigger()` in `airflow-ctl/src/airflowctl/api/operations.py` serializes the request body without `exclude_none=True`: ```python json=trigger_dag_run.model_dump(mode="json") ``` `TriggerDAGRunPostBody` includes `partition_key` and `bundle_version`, both added in Airflow 3.2.0's model. Since these default to `None` and are never excluded from serialization, every trigger request includes them as `null` regardless of the target server's Airflow version. Any server running < 3.2.0 doesn't recognize these fields and rejects the request entirely. `AssetsOperations.create_event()` in the same file already handles this correctly: ```python json=asset_event_body.model_dump(mode="json", exclude_none=True) ``` Confirmed via the live OpenAPI schema on a 3.1.x deployment (`curl .../openapi.json`) that `partition_key`/`bundle_version` genuinely don't exist in that server's `TriggerDAGRunPostBody` schema, and confirmed directly against the `apache/airflow` source that these fields were added starting at the `3.2.0` tag (absent in `3.1.0` through `3.1.8`). ### What is the expected results? `airflowctl dags trigger` should succeed against any Airflow API server version whose `TriggerDAGRunPostBody` schema it's compatible with, i.e., it shouldn't send fields the target server doesn't recognize just because the client's own model happens to declare them, when those fields were never explicitly set by the caller. ### Anything else? Steps to reproduce: 1. Deploy Airflow 3.1.x (rep…