Split migrations folder (#21549)

There are too many files in `models/migrations` folder so that I split
them into sub folders.

models/migrations/v1_18/v228.go

@@ -0,0 +1,26 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package v1_18 // nolint
+
+import (
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+)
+
+func AddTeamInviteTable(x *xorm.Engine) error {
+	type TeamInvite struct {
+		ID          int64              `xorm:"pk autoincr"`
+		Token       string             `xorm:"UNIQUE(token) INDEX NOT NULL DEFAULT ''"`
+		InviterID   int64              `xorm:"NOT NULL DEFAULT 0"`
+		OrgID       int64              `xorm:"INDEX NOT NULL DEFAULT 0"`
+		TeamID      int64              `xorm:"UNIQUE(team_mail) INDEX NOT NULL DEFAULT 0"`
+		Email       string             `xorm:"UNIQUE(team_mail) NOT NULL DEFAULT ''"`
+		CreatedUnix timeutil.TimeStamp `xorm:"INDEX created"`
+		UpdatedUnix timeutil.TimeStamp `xorm:"INDEX updated"`
+	}
+
+	return x.Sync2(new(TeamInvite))
+}