Log request (and response) in single batch

Feign's Logger is logging once per request / response line item.
For example, JavaLogger will log the following request / response pair by invoking java.util.logging.Logger 7 times:

[SendsStuff#login] ---> POST http://localhost:61113/ HTTP/1.1
[SendsStuff#login] Content-Length: 80
[SendsStuff#login] Content-Type: application/json
[SendsStuff#login] ---> END HTTP (80-byte body)
[SendsStuff#login] <--- HTTP/1.1 200 OK (1ms)
[SendsStuff#login] content-length: 3
[SendsStuff#login] <--- END HTTP (3-byte body)

Currently, in a Kibana + Logstash environment, these log line are scattered, having one document per log line. The logs for one single request are scattered in different documents. The same goes for the response. Thus, it's difficult to follow the logs.

What I'm suggesting is to have some sort of log batching, such that we end up with one log call for the request, another for the response. Having a single log per request/response means having a single document for request, another for response. That would be much easier to follow.

Start with Feign's Logger and JavaLogger entry points described in the issue, and trace how request and response line items are emitted. Compare the current per-line calls with the desired request and response boundaries. Done means each request and response is emitted through one log call while retaining the shown information.