It would be useful to have an option to use the headers sent alongside the request that triggers the deployment webhook.
This is an extension of https://roadmap.ploi.io/projects/2-site-level-requests/items/1009-make-data-send-to-the-deploy-webhook-url-available-as-deploy-script-variable
It also seems like an extension of https://roadmap.ploi.io/projects/2-site-level-requests/items/1518-deploy-script-variable-to-check-which-webhook-was-used, but I think this issue covers another scenario.
Why would you want to have this as header support? Why not use POST BODY which is already supported?
https://ploi.io/documentation/deployment/how-to-use-the-deploy-webhook-url
Other systems do not always provide the option to configure the body to put information inside the "variables" property, but some do provide the option to send custom headers.
Another option would be to let the user decide which property path should be used to find variables, but I can imagine that's more work or has some security concerns.
This feature would contribute to a wider integration of other systems by making the webhook configuration more flexible.
