feat: add invitation and promotion functions

api/store/model/invite_code.go

@@ -0,0 +1,12 @@
+package model
+
+import "time"
+
+type InviteCode struct {
+	Id        uint `gorm:"primarykey;column:id"`
+	UserId    uint
+	Code      string
+	Hits      int // 点击次数
+	RegNum    int // 注册人数
+	CreatedAt time.Time
+}

api/store/model/invite_log.go

@@ -0,0 +1,15 @@
+package model
+
+import (
+	"time"
+)
+
+type InviteLog struct {
+	Id         uint `gorm:"primarykey;column:id"`
+	InviterId  uint
+	UserId     uint
+	Username   string
+	InviteCode string
+	Reward     string `gorm:"column:reward_json"` // 邀请奖励
+	CreatedAt  time.Time
+}