Webhook behavior customization and delivery records

[tdruez]

This PR expands on the existing WebhookSubscription model by adding a few fields to configure the behavior of the Webhook, and moving some of the fields to a new WebhookDelivery model, which captures the results of a WebhookSubscription "delivery".

@JonoYang Could you give it a try and see if the current addition would work for your needs in the context of the PurlDB workers?

For example, adding a Webhook from the code:

project.add_webhook_subscription(
    target_url="URL",
    trigger_on_each_run=False,
    include_summary=True,
    include_results=True,
)

Also available using the API:

data = {
    "name": "Project1",
    "webhooks": [
        {
            "target_url": "URL",
            "trigger_on_each_run": False,
            "include_summary": True,
            "include_results": True,
            "is_active": True,
        }
    ],
}

[JonoYang]

The updates look good and I'm able to use the new webhook subscriptions, but I'm running into a problem with authentication when sending the results back to purldb.

[JonoYang]

I am having trouble sending the project results back to purldb because the authentication token is not used here.