Add solver HTTP traces

[bgins]

We would like to collect more information about HTTP requests made to the solver server. This data can give us information about frequency of requests, status codes, failed requests and more.

Let's see if we can add https://pkg.go.dev/go.opentelemetry.io/contrib/instrumentation/github.com/gorilla/mux/otelmux as a middleware on our router. We can send traces to our existing observability infrastructure.