Init V4 community edition (#2265)

* Init V4 community edition

* Init V4 community edition

application/migrator/model/folder.go

@@ -0,0 +1,18 @@
+package model
+
+import (
+	"github.com/jinzhu/gorm"
+)
+
+// Folder 目录
+type Folder struct {
+	// 表字段
+	gorm.Model
+	Name     string `gorm:"unique_index:idx_only_one_name"`
+	ParentID *uint  `gorm:"index:parent_id;unique_index:idx_only_one_name"`
+	OwnerID  uint   `gorm:"index:owner_id"`
+
+	// 数据库忽略字段
+	Position      string `gorm:"-"`
+	WebdavDstName string `gorm:"-"`
+}