Add Content-Type header to Form Webhook

[AndreasCaldewei]

Is your feature request related to a problem? Please describe.

Currently, there is no option to set headers on the Form Webhook. I need to set a Content-Type header on the request to properly integrate with a CRM.

https://github.com/webiny/webiny-js/blob/0581a6e48ce328e3a5f50216745bccc4afb8e1be/packages/api-form-builder/src/plugins/triggers/webhook.ts#L21-L32

Describe the feature's behavior.

Two possible solutions are:

• Set a default Content-Type header to 'application/json'
• Make the headers customizable, allowing users to set their own headers, by passing trough an object like headers in the plugin.

Describe alternatives you've considered.

No response