Add solver HTTP rate limiting

[bgins]

We have noticed the solver may receive unbounded requests from job creators or resource providers. Let's add a rate limiter to limit traffic to an acceptable threshold.

We can start with a simple policy to set a limit by IP address and route. For example we could use go-chi/httprate: https://github.com/go-chi/httprate#rate-limit-by-ip-and-url-path-aka-endpoint.

[walkerlj0]

@kelindi to review @bgins PR for adding rate limiting