Add migrate from OneDev (#16356)

* Use context to simplify logic.

* Added migration from OneDev.
This PR adds [OneDev](https://code.onedev.io/) as migration source.

Supported:
- [x] Milestones
- [x] Issues
- [x] Pull Requests
- [x] Comments
- [x] Reviews
- [x] Labels

modules/migrations/base/downloader.go

@@ -13,9 +13,9 @@ import (
 
 // GetCommentOptions represents an options for get comment
 type GetCommentOptions struct {
-	IssueNumber int64
-	Page        int
-	PageSize    int
+	Context  IssueContext
+	Page     int
+	PageSize int
 }
 
 // Downloader downloads the site repo information
@@ -30,7 +30,7 @@ type Downloader interface {
 	GetComments(opts GetCommentOptions) ([]*Comment, bool, error)
 	SupportGetRepoComments() bool
 	GetPullRequests(page, perPage int) ([]*PullRequest, bool, error)
-	GetReviews(pullRequestNumber int64) ([]*Review, error)
+	GetReviews(pullRequestContext IssueContext) ([]*Review, error)
 	FormatCloneURL(opts MigrateOptions, remoteAddr string) (string, error)
 }