Allow customization of the webhook payload

Problem Statement

One can already configure a webhook for a form in Baserow (which partly solves https://gitlab.com/bramw/baserow/-/issues/206), but the request payload is always defined through Baserow itself. For easier integration into other systems it would be create if admins could format/customize the payload.

Who will benefit?

Admins trying to integration Baserow into other systems. Use cases: sign up a user to an external service.

Benefits and risks

What benefits does this bring?
    - easier integration into other systems, which require an exactly formatted request body
    
What risks might this introduce?
    - admins could misformat request bodies

Proposed solution

Make the "Example payload" field editable, will probably require the use of variables.

Examples

Current payload is:

{
    "table_id": 107,
    "event_type": "row.created",
    "event_id": "00000000-0000-0000-0000-000000000000",
    "row_id": 0,
    "values": {
        "id": 0,
        "order": "1.00000000000000000000",
        "Name": "",
        "E-Mail": "",
        "Terms & Conditions": false
    }
}

But I want to be able to send:

{
  "email": "string@domain.com",
  "username": "string",
  "displayName": "string",
  "password": "string",
  "admin": false
}

UI/UX Design Required

  • Substantial (This involves the creation of entirely new pages, layouts, many new components which don't exist in the style guide)
  • Some (Mainly involves re-use or duplication of existing UI components with minimal customization)
  • None (No UI/UX work required for this feature)

Priority/Severity

  • High (This will bring a huge increase in performance/productivity/usability/legislative cover)
  • Medium (This will bring a good increase in performance/productivity/usability)
  • Low (anything else e.g., trivial, minor improvements)