Make readiness state of EPP dependant on availability of NATS (#49)

* Make readiness state of EPP dependant on availability of NATS

* Sort imports

pkg/sender/jetstream/health.go

@@ -3,13 +3,20 @@ package jetstream
 import (
 	"net/http"
 
+	"github.com/nats-io/nats.go"
+
 	"github.com/kyma-project/eventing-publisher-proxy/pkg/handler/health"
 )
 
 // ReadinessCheck returns an instance of http.HandlerFunc that checks the readiness of the given NATS Handler.
 // It checks the NATS server connection status and reports 2XX if connected, otherwise reports 5XX.
 // It panics if the given NATS Handler is nil.
 func (s *Sender) ReadinessCheck(w http.ResponseWriter, _ *http.Request) {
+	if status := s.ConnectionStatus(); status != nats.CONNECTED {
+		s.namedLogger().Error("Readiness check failed: not connected to nats server")
+		w.WriteHeader(health.StatusCodeNotHealthy)
+		return
+	}
 	w.WriteHeader(health.StatusCodeHealthy)
 }