### What do you see as an issue?

The [/dags/{dag_id}/details](https://airflow.apache.org/docs/apache-airflow/stable/stable-rest-api-ref.html#operation/post_set_task_instances_state) endpoint of the REST API does not return all of the keys that are listed in the documentation. If I run `curl -X GET localhost:8080/api/v1/dags/{my_dag}/details`, then compare the results with the results in the documentation, you can see the following missing keys:

```python
>>> for key in docs.keys():
...     if not key in actual.keys():
...             print(key)
...
root_dag_id
last_parsed_time
last_pickled
last_expired
scheduler_lock
timetable_description
has_task_concurrency_limits
has_import_errors
next_dagrun
next_dagrun_data_interval_start
next_dagrun_data_interval_end
next_dagrun_create_after
template_search_path
```

### Solving the problem

Either remove these keys from the documentation or fix the API endpoint

### Anything else

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

:param run_id: ID of the DAG run to get the task concurrency of
        :param task_ids: A list of valid task IDs for the given DAG
        :param states: A list of states to filter by if supplied
        :return: The number of running tasks
        """
        qry = select(func.count(TaskInstance.task_id)).where(
            TaskInstance.dag_id == dag_id,
        )
        if run_id:
            qry = qry.where(
                TaskInstance.run_id == run_id,
            )
        if task_ids:
            qry = qry.where(
                TaskInstance.task_id.in_(task_ids),
            )
        if states:
            if None in states:
                if all(x is None for x in states):
                    qry = qry.where(TaskInstance.state.is_(None))
                else:
                    not_none_states = [state for state in states if state]
                    qry = qry.where(
                        or_(TaskInstance.state.in_(not_none_states), TaskInstance.state.is_(None))
                    )
            else:
                qry = qry.where(TaskInstance.state.in_(states))
        return session.scalar(qry)
    @classmethod
    def get_serialized_fields(cls):