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

* Move migrtions into services and base into modules/migration

* Fix imports

* Fix lint

modules/migration/review.go

@@ -0,0 +1,45 @@
+// Copyright 2019 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 migration
+
+import "time"
+
+// enumerate all review states
+const (
+	ReviewStatePending          = "PENDING"
+	ReviewStateApproved         = "APPROVED"
+	ReviewStateChangesRequested = "CHANGES_REQUESTED"
+	ReviewStateCommented        = "COMMENTED"
+)
+
+// Review is a standard review information
+type Review struct {
+	ID           int64
+	IssueIndex   int64  `yaml:"issue_index"`
+	ReviewerID   int64  `yaml:"reviewer_id"`
+	ReviewerName string `yaml:"reviewer_name"`
+	Official     bool
+	CommitID     string `yaml:"commit_id"`
+	Content      string
+	CreatedAt    time.Time `yaml:"created_at"`
+	State        string    // PENDING, APPROVED, REQUEST_CHANGES, or COMMENT
+	Comments     []*ReviewComment
+}
+
+// ReviewComment represents a review comment
+type ReviewComment struct {
+	ID        int64
+	InReplyTo int64 `yaml:"in_reply_to"`
+	Content   string
+	TreePath  string `yaml:"tree_path"`
+	DiffHunk  string `yaml:"diff_hunk"`
+	Position  int
+	Line      int
+	CommitID  string `yaml:"commit_id"`
+	PosterID  int64  `yaml:"poster_id"`
+	Reactions []*Reaction
+	CreatedAt time.Time `yaml:"created_at"`
+	UpdatedAt time.Time `yaml:"updated_at"`
+}