Add auth protection sample and standardize json.

backend/internal/middleware/auth.go

@@ -0,0 +1,24 @@
+package middleware
+
+import (
+	"net/http"
+
+	"starter/backend/internal/handlers"
+
+	"github.com/gin-contrib/sessions"
+	"github.com/gin-gonic/gin"
+	"github.com/logto-io/go/client"
+)
+
+// AuthRequired 是 Logto 认证中间件，未认证用户返回 401
+func AuthRequired() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		session := sessions.Default(c)
+		logtoClient := client.NewLogtoClient(handlers.GetLogtoConfig(), &handlers.SessionStorage{Session: session})
+		if !logtoClient.IsAuthenticated() {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "unauthorized"})
+			return
+		}
+		c.Next()
+	}
+}