fix: add valid origin check for cors (#83)

Resolves #72

server/middlewares/cors.go

@@ -0,0 +1,29 @@
+package middlewares
+
+import (
+	"github.com/authorizerdev/authorizer/server/constants"
+	"github.com/authorizerdev/authorizer/server/utils"
+	"github.com/gin-gonic/gin"
+)
+
+func CORSMiddleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		origin := c.Request.Header.Get("Origin")
+		constants.APP_URL = origin
+
+		if utils.IsValidOrigin(origin) {
+			c.Writer.Header().Set("Access-Control-Allow-Origin", origin)
+		}
+
+		c.Writer.Header().Set("Access-Control-Allow-Credentials", "true")
+		c.Writer.Header().Set("Access-Control-Allow-Headers", "Content-Type, Content-Length, Accept-Encoding, X-CSRF-Token, Authorization, accept, origin, Cache-Control, X-Requested-With")
+		c.Writer.Header().Set("Access-Control-Allow-Methods", "POST, OPTIONS, GET, PUT")
+
+		if c.Request.Method == "OPTIONS" {
+			c.AbortWithStatus(204)
+			return
+		}
+
+		c.Next()
+	}
+}