add MIT license and rename health handler file

Add the MIT license file and rename the health handler to follow the project's naming convention for route files.

internal/handlers/health.route.go

@@ -0,0 +1,27 @@
+package handlers
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"time"
+
+	"github.com/jmoiron/sqlx"
+)
+
+func Health(db *sqlx.DB) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		ctx, cancel := context.WithTimeout(r.Context(), 3*time.Second)
+		defer cancel()
+
+		w.Header().Set("Content-Type", "application/json")
+
+		if err := db.PingContext(ctx); err != nil {
+			w.WriteHeader(http.StatusServiceUnavailable)
+			json.NewEncoder(w).Encode(map[string]string{"status": "ok", "db": "error"})
+			return
+		}
+
+		json.NewEncoder(w).Encode(map[string]string{"status": "ok", "db": "ok"})
+	}
+}