CHW-4103 InvalidPayload

request payload was missing or malformed; see endpoint documentation for the expected JSON shape

Default message: request payload was missing or malformed; see endpoint documentation for the expected JSON shape
HTTP status: 400 (client)

Problem. The request body was missing, empty, or not parseable as JSON. Cause. The client sent Content-Type: application/json but no body, or a malformed body. Fix. Re-serialise the payload per the endpoint’s documented shape. HTTP 400.