API GW logging "Endpoint request body" in all requests, even 4xx and 5xx.

Invalid API Keys or Quota exceptions will raise errors before reaching the content validation phase of your request (as well as transformation and mappings), thus not being able to capture the payload.

Customer can still enrich their logs using Custom Access Logs instead of just using plain Execution Logs, but that won't suffice for the case of errors in the Invalid API cases.

You can check the available attributes for the $context variable for Custom Access Logging here: https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html#context-variable-reference