feat: middleware for request body parsing, validation and authentication;

feat: helper function for getting request info from gin context

backend/internal/middleware/request.go

@@ -43,13 +43,21 @@ func UserInfoFromContext(c *gin.Context) (*UserInfo, bool) {
 	var ok bool
 
 	username, ok = c.Get("username") ; if !ok {
-     return nil, true
+     return &UserInfo{Username: "", Role: enums.GuestRole}, true
 	}
 
 	role, ok = c.Get("role"); if !ok {
      return nil, false
 	}
 
+	if username == nil {
+     return &UserInfo{Username: "", Role: enums.GuestRole}, true
+	}
+
+	if role == nil {
+		return nil, false
+	}
+
 	return &UserInfo{Username: username.(string), Role: role.(enums.Role)}, true
 }
 
@@ -67,9 +75,13 @@ func RequestMiddleware[T any](role enums.Role) gin.HandlerFunc {
 			return
 		}
 
+		if userInfo.Role < role {
+			c.Status(http.StatusForbidden)
+		}
+
 		var body T
 		if err := c.ShouldBindJSON(&body); err != nil {
-			c.JSON(http.StatusBadRequest, err)
+			c.String(http.StatusBadRequest, err.Error())
 
 			// TODO: implement automatic validation here
 			return