Add support for arrays of different data types in the Trigger Form UI

[MatthieuBlais]

Description

The new Trigger Form UI released in 2.6 is handy but doesn't support array params of data types other than string. For more flexibility, this PR proposes to generate a JSON field similar to the object param if the users specify the attribute items in schema.

How to reproduce the issue

Use an array param and require the items to be integers.

with DAG(
    dag_id=Path(__file__).stem,
    description=__doc__[0 : __doc__.find(".")],
    doc_md=__doc__,
    schedule=None,
    start_date=datetime.datetime(2022, 3, 4),
    catchup=False,
    tags=["example_ui"],
    params={
        "array_of_numbers": Param(
            [1, 2, 3],
            "Only integers are accepted in this array",
            type="array",
            title="Array of numbers",
            items={"type": "number"},
        ),
    },
) as dag:

    @task(task_id="show_params")
    def show_params(**kwargs) -> None:
        ti: TaskInstance = kwargs["ti"]
        dag_run: DagRun = ti.dag_run
        if not dag_run.conf:
            print("Uups, no parameters supplied as DagRun.conf, was the trigger w/o form?")
            raise AirflowSkipException("No DagRun.conf parameters supplied.")
        print(f"This DAG was triggered with the following parameters:\n{json.dumps(dag_run.conf, indent=4)}")

    show_params()

The Generated Conf JSON shows an array of strings

And we cannot trigger the DAG:

Workaround

We can manually update the Generated Configuration JSON box, but it is not user friendly (especially if we expect an array of objects!), and will become counter intuitive as users get used to the benefits of the new trigger form.

What do you think @jens-scheffler-bosch ?

[jscheffl]

Just some small beautification proposals in documentation, otherwise - I like it! Thanks for the contribution!
(Take my approval emotional, I have no committer status)

[MatthieuBlais]

Great, thanks for the feedback! I've updated the PR with your commits

[jscheffl]

Great, thanks for the feedback! I've updated the PR with your commits

Uuups, sorry, my comments were not syntax checked :-( The URL is not correctly formed to be accepted by Sphinx.