Implement s3 storage.

Use uuid as file id.

server/dao/storage.go

@@ -1,6 +1,10 @@
 package dao
 
-import "nysoure/server/model"
+import (
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+	"nysoure/server/model"
+)
 
 func CreateStorage(s model.Storage) (model.Storage, error) {
 	err := db.Model(&s).Create(&s).Error
@@ -22,3 +26,14 @@ func GetStorage(id uint) (model.Storage, error) {
 	err := db.Model(&model.Storage{}).Where("id = ?", id).First(&storage).Error
 	return storage, err
 }
+
+func AddStorageUsage(id uint, offset int64) error {
+	return db.Transaction(func(tx *gorm.DB) error {
+		var storage model.Storage
+		err := tx.Clauses(clause.Locking{Strength: clause.LockingStrengthUpdate}).Model(&model.Storage{}).Where("id = ?", id).First(&storage).Error
+		if err != nil {
+			return err
+		}
+		return tx.Model(&model.Storage{}).Where("id = ?", id).Update("current_size", storage.CurrentSize+offset).Error
+	})
+}