Split migrations folder (#21549)

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

models/migrations/v1_16/v205.go

@@ -0,0 +1,43 @@
+// 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_16 //nolint
+
+import (
+	"code.gitea.io/gitea/models/migrations/base"
+
+	"xorm.io/xorm"
+	"xorm.io/xorm/schemas"
+)
+
+func MigrateUserPasswordSalt(x *xorm.Engine) error {
+	dbType := x.Dialect().URI().DBType
+	// For SQLITE, the max length doesn't matter.
+	if dbType == schemas.SQLITE {
+		return nil
+	}
+
+	if err := base.ModifyColumn(x, "user", &schemas.Column{
+		Name: "rands",
+		SQLType: schemas.SQLType{
+			Name: "VARCHAR",
+		},
+		Length: 32,
+		// MySQL will like us again.
+		Nullable:       true,
+		DefaultIsEmpty: true,
+	}); err != nil {
+		return err
+	}
+
+	return base.ModifyColumn(x, "user", &schemas.Column{
+		Name: "salt",
+		SQLType: schemas.SQLType{
+			Name: "VARCHAR",
+		},
+		Length:         32,
+		Nullable:       true,
+		DefaultIsEmpty: true,
+	})
+}