ClientFlow should allow for environment-specific configuration

[akara]

Such configuration should be recognized by ClientFlow:

svc1 {
  type = squbs.httpclient
  akka.http.host-connection-pool {
    max-connections = 10
  }

  QA {
    // Any standard configuration
    akka.http.host-connection-pool {
      max-connections = 2
    }
  }
}

[anilgursel]

I tend to disagree with this issue. We have EnvironmentResolver which could be used to customize configuration per environment. Baking this functionality directly into ClientFlow does not sound right to me.