feat: being able to add headers template in webhooks created dynamically

[gaelloyoly]

Add usage of headers template
https://docs.apify.com/platform/integrations/webhooks/actions#headers-template

[Pijukatel]

@gaelloyoly Hello, thank for the PR. Just to help me understand the context of the change. In what situation do you get "headers_template" key in that dictionary? In other workds, why is it not 'headersTemplate' directly?

[gaelloyoly]

@Pijukatel I wanted to create an ad-hoc webhook and I followed the example by passing a dict with payloadTemplate and headerTemplate but none of them was used.
Then I saw that the Webhook data structure in python is using underscores : https://docs.apify.com/sdk/python/reference/class/Webhook
I guess it's to make it more "pythonic". That's why I'm using this for headers too.

[Pijukatel]

@gaelloyoly Could you please describe your top level call (Which client did you use, or did you call some Actor method from Apify SDK?) Because I see, that there is a function that is already responsible for conversion from underscore names: https://github.com/apify/apify-client-python/blob/master/src/apify_client/clients/resource_clients/webhook.py#L24
, but most likely there is some path that is not using this function, so that is why I want to understand how you called it.

[gaelloyoly]

Yes, it's the "start" method of the actor client. I'm doing something like this :

from apify_client import ApifyClient
client = ApifyClient("APIFY_API_KEY")
client.actor("actor_id").start(
    run_input={"url": "input_url"},
    webhooks=[{
        "event_types": ["ACTOR.RUN.SUCCEEDED"],
        "request_url": "https://example.com/success",
        "payload_template": "{{resource}}",
        "headers_template": '{"x-custom-signature": "1234567890"}',
    }],
)