refactor: use dependency injection in backend

backend/internal/middleware/cors.go

@@ -0,0 +1,24 @@
+package middleware
+
+import (
+	"github.com/stonith404/pocket-id/backend/internal/common"
+	"time"
+
+	"github.com/gin-contrib/cors"
+	"github.com/gin-gonic/gin"
+)
+
+type CorsMiddleware struct{}
+
+func NewCorsMiddleware() *CorsMiddleware {
+	return &CorsMiddleware{}
+}
+
+func (m *CorsMiddleware) Add() gin.HandlerFunc {
+	return cors.New(cors.Config{
+		AllowOrigins: []string{common.EnvConfig.AppURL},
+		AllowMethods: []string{"*"},
+		AllowHeaders: []string{"*"},
+		MaxAge:       12 * time.Hour,
+	})
+}