feat(health): add health checking endpoints and logic

Introduce health checking functionality with liveness and readiness 
endpoints to monitor the application's status. Implement a health 
checker that verifies database connectivity and provides a simple 
liveness check. Update service routing to use the new health 
checker functionality. Add corresponding unit tests for validation.

cmd/service/service.go

@@ -30,6 +30,7 @@ import (
 	"gitlab.com/unboundsoftware/schemas/domain"
 	"gitlab.com/unboundsoftware/schemas/graph"
 	"gitlab.com/unboundsoftware/schemas/graph/generated"
+	"gitlab.com/unboundsoftware/schemas/health"
 	"gitlab.com/unboundsoftware/schemas/logging"
 	"gitlab.com/unboundsoftware/schemas/middleware"
 	"gitlab.com/unboundsoftware/schemas/monitoring"
@@ -241,8 +242,12 @@ func start(closeEvents chan error, logger *slog.Logger, connectToAmqpFunc func(u
 			Cache: lru.New[string](100),
 		})
 
+		healthChecker := health.New(db.DB, logger)
+
 		mux.Handle("/", monitoring.Handler(playground.Handler("GraphQL playground", "/query")))
-		mux.Handle("/health", http.HandlerFunc(healthFunc))
+		mux.Handle("/health", http.HandlerFunc(healthChecker.LivenessHandler))
+		mux.Handle("/health/live", http.HandlerFunc(healthChecker.LivenessHandler))
+		mux.Handle("/health/ready", http.HandlerFunc(healthChecker.ReadinessHandler))
 		mux.Handle("/query", cors.AllowAll().Handler(
 			monitoring.Handler(
 				mw.Middleware().CheckJWT(
@@ -301,10 +306,6 @@ func loadSubGraphs(ctx context.Context, eventStore eventsourced.EventStore, serv
 	return nil
 }
 
-func healthFunc(w http.ResponseWriter, _ *http.Request) {
-	_, _ = w.Write([]byte("OK"))
-}
-
 func ConnectAMQP(url string) (Connection, error) {
 	return goamqp.NewFromURL(serviceName, url)
 }