gqltest: allow writing of request and response bodies to a sink
Created by: Strum355
Allow defining sinks for request/response bodies in the gqltest client for GraphQL requests only, not direct Get/Post requests, as they return the raw *http.Response
, so users can do their own logging there.
Part of the grander "why is codeintel QA flaking" effort
Test plan
Running a main-dry-run pipeline here: https://buildkite.com/sourcegraph/sourcegraph/builds/160829