nix(loadtest): additionally group results by status code and method

This gives us a much better idea immediately when looking at the report.
It also allows us to differentiate between different return codes on the
same URI, which might come in handy when dealing with expired JWT and
such.

A nice side-effect: All the error-related requests are now grouped
together in the 4xx section.

Author: wolfgangwalther

nix/tools/loadtest.nix

@@ -260,7 +260,7 @@ let
       }
       ''
         ${vegeta}/bin/vegeta encode "$_arg_file" \
-          | ${jq}/bin/jq --slurp 'map(select(.url != "")) | group_by(.url) | map({(.[0].url | sub("^http://postgrest";"")): map(.latency) | min / 10e3 }) | .[]' \
+          | ${jq}/bin/jq --slurp 'map(select(.url != "")) | group_by("\(.code) \(.method) \(.url)") | map({("\(.[0].code) \(.[0].method) \(.[0].url)" | sub("http://postgrest";"")): map(.latency) | min / 10e3 }) | .[]' \
           | ${jq}/bin/jq --arg branch "$(basename "$_arg_file" .bin)" '. + {branch: $branch}'
       '';