feat: add async discord notifier

[dondaum]

Add an asynchronous version of DiscordNotifier.

related: #55237

I sucessfully tested the DiscordNotifier with the following Dag:

from datetime import timedelta
from airflow import DAG
from airflow.sdk.definitions.deadline import AsyncCallback, DeadlineAlert, DeadlineReference
from airflow.providers.discord.notifications.discord import DiscordNotifier
from airflow.providers.standard.operators.empty import EmptyOperator
from airflow.sdk import task

with DAG(
    dag_id="deadline_discord_alert_example",
    deadline=DeadlineAlert(
        reference=DeadlineReference.DAGRUN_QUEUED_AT,
        interval=timedelta(seconds=20),
        callback=AsyncCallback(
            DiscordNotifier,
            kwargs={
                "text": "🚨 Dag {{ dag_run.dag_id }} missed deadline at {{ deadline.deadline_time }}. DagRun: {{ dag_run }}",
            },
        ),
    ),
):
    c = EmptyOperator(task_id="example_task")

    @task()
    def wait():
        import time
        time.sleep(60*5)

    
    c >> wait()

---

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[ferruzzi]

Looks like you have a handful of comments already, so I'll let things settle a bit before I review, but feel free to ping me when you are ready. As always, thanks for the work!

[Lee-W]

We still need some work to make the CI green. Mark it as draft before it's ready to review again. Thanks!

[dondaum]

CI is green now.

In my opinion, it makes sense to continue with this feature if it looks good.

Yes, the backwards compatible part is redundant with #57143, but in my opinion we could add it to our open items list and change all providers to use the common-provider once #57143 is merged.

WDYT ? @ferruzzi @ramitkataria

[ferruzzi]

we could add it to our open items list and change all providers to use the common-provider once #57143 is merged.

I'm not thrilled with how many todos we're leaving hanging, but I guess that's life. Resolve the comments that are resolved and I'll make a pass tomorrow.

[ferruzzi]

Merged #57143, let's get this one wrapped now!

@dondaum - Let us know when you've cleaned it up and are ready for another round of reviews.

[Lee-W]

I'll mark it as draft. But please let us know when it's ready again. Looking forward to this one!

[dondaum]

we could add it to our open items list and change all providers to use the common-provider once #57143 is merged.

I'm not thrilled with how many todos we're leaving hanging, but I guess that's life. Resolve the comments that are resolved and I'll make a pass tomorrow.

Let's reduce our list of open items. I have opened a PR for the Slack provider for use airflow.providers.common.compat #57894

[dondaum]

Thank you for all the patience and support. I'm opening it up for another round of reviews.

[ferruzzi]

Let's reduce our list of open items. I have opened a PR for the Slack provider for use airflow.providers.common.compat #57894

To be clear, that wasn't a jab at you by any means. Just in case it came off the wrong way. I greatly appreciate your work on these and hope I didn't imply otherwise.

[dondaum]

Let's reduce our list of open items. I have opened a PR for the Slack provider for use airflow.providers.common.compat #57894

To be clear, that wasn't a jab at you by any means. Just in case it came off the wrong way. I greatly appreciate your work on these and hope I didn't imply otherwise.

Don't worry, I got it right. I like keeping things clean and I consider myself to have an intrinsic motivation to clean up my own things.

[dondaum]

Is there anything I can do to move forward with this PR?

[Lee-W]

Will take a look tomorrow.

[Lee-W]

mostly good, a nit and a typo.

[Lee-W]

Approve as the remaining one is a nitpick. @dondaum, please click resolve for the comments you think you've already resolved :)

[Lee-W]

I'll keep it open for a few days so that other can take a look. But overall looks good! Thanks!

[jason810496]

Thanks for the PR! LGTM to me overall !