Move migrations into services and base into modules/migration (#17663)

* Move migrtions into services and base into modules/migration

* Fix imports

* Fix lint

services/migrations/error.go

@@ -0,0 +1,29 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Copyright 2018 Jonas Franz. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"errors"
+
+	"github.com/google/go-github/v39/github"
+)
+
+var (
+	// ErrRepoNotCreated returns the error that repository not created
+	ErrRepoNotCreated = errors.New("repository is not created yet")
+)
+
+// IsRateLimitError returns true if the err is github.RateLimitError
+func IsRateLimitError(err error) bool {
+	_, ok := err.(*github.RateLimitError)
+	return ok
+}
+
+// IsTwoFactorAuthError returns true if the err is github.TwoFactorAuthError
+func IsTwoFactorAuthError(err error) bool {
+	_, ok := err.(*github.TwoFactorAuthError)
+	return ok
+}