Add Support for Advance Labels ( LabelV2)

Add Support for Custom Migration to keep supporting two database( sqlite and postgres)
Migration from Label to LabelV2

internal/label/model/model.go

@@ -0,0 +1,9 @@
+package model
+
+type Label struct {
+	ID        int    `json:"id" gorm:"primary_key"`
+	Name      string `json:"name" gorm:"column:name"`
+	Color     string `json:"color" gorm:"column:color"`
+	CircleID  *int   `json:"-" gorm:"column:circle_id"`
+	CreatedBy int    `json:"created_by" gorm:"column:created_by"`
+}