Filter on payload attributes' value #51

(this is a TLDR, I can develop the idea if accepted)

Problem

Our SaaS event webhooks are plugged to some of our clients' low/no-code platform. They pay per execution.
They want to save unecessary execution by filtering events upstream with simple conditions.

The way to solve it today

• Create a label to mirror attribute value (ie : "paid") to enable filtering.
  or
• Filter event trigger on our side based on payload value.

Proposed solution

Introduce a filter declaration at subscription creation.

Something like :

{
  "payload_filter": {
    "all": [              #or "any"
      { "path": "status", "op": "eq", "value": "paid" },
      { "path": "amount", "op": "gt", "value": 1000 }
    ]
  }
}

Impacts

• API interface
• Event matching logic : additionnaly to event_type & labels, add payload_filter evaluation.

Afterthoughts:

• this filtering format only works with json ==> what would match wider range of payload format? RegEx ?