Description:
Often external authorization service needs the message body to authorize a request, for example when doing HMAC validation. Making the request data available to the authorization service could be achieved by buffering the request data inside envoy.ext_authz and then adding it to the authorization request.

The buffering mechanism would work similarly to envoy.buffer filter which HTTP 413 when the buffer reaches the max_request_bytes. Buffer config should be optional and disabled by default.