JSON Schema validation for data used by Gitea during migrations

Discussion at https://forum.forgefriends.org/t/common-json-schema-for-repository-information/563

Co-authored-by: Loïc Dachary <loic@dachary.org>

* Move migrtions into services and base into modules/migration

* Fix imports

* Fix lint

* 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

* Dump github/gitlab repository data to a local directory

* Fix lint

* Adjust directory structure

* Allow migration special units

* Allow migration ignore release assets

* Fix lint

* Add restore repository

* stage the changes

* Merge

* Fix lint

* Update the interface

* Add some restore methods

* Finish restore

* Add comments

* Fix restore

* Add a token flag

* Fix bug

* Fix test

* Fix test

* Fix bug

* Fix bug

* Fix lint

* Fix restore

* refactor downloader

* fmt

* Fix bug isEnd detection on getIssues

* Refactor maxPerPage

* Remove unused codes

* Remove unused codes

* Fix bug

* Fix restore

* Fix dump

* Uploader should not depend downloader

* use release attachment name but not id

* Fix restore bug

* Fix lint

* Fix restore bug

* Add a method of DownloadFunc for base.Release to make uploader not depend on downloader

* fix Release yml marshal

* Fix trace information

* Fix bug when dump & restore

* Save relative path on yml file

* Fix bug

* Use relative path

* Update docs

* Use git service string but not int

* Recognize clone addr to service type

* Add Ref to api.Issue

This PR adds Ref to api.Issue and adds the backend parts to the migrator.

Fix #13918

Signed-off-by: Andrew Thornton <art27@cantab.net>

* first draft

* update gitea sdk to 9e280adb4d

* adapt feat of updated sdk

* releases now works

* break the Reactions loop

* use convertGiteaLabel

* fix endless loop because paggination is not supported there !!!

* rename gitea local uploader files

* pagination can bite you in the ass

* Version Checks

* lint

* docs

* rename gitea sdk import to miss future conficts

* go-swagger: dont scan the sdk structs

* make sure gitea can shutdown gracefully

* make GetPullRequests and GetIssues similar

* rm useles

* Add Test: started ...

* ... add tests ...

* Add tests and Fixing things

* Workaround missing SHA

* Adapt: Ensure that all migration requests are cancellable
(714ab71ddc)

* LINT: fix misspells in test set

* adapt ListMergeRequestAwardEmoji

* update sdk

* Return error when creating giteadownloader failed

* update sdk

* adapt new sdk

* adopt new features

* check version before err

* adapt: 'migrate service type switch page'

* optimize

* Fix DefaultBranch

* impruve

* handle subPath

* fix test

* Fix ReviewCommentPosition

* test GetReviews

* add DefaultBranch int test set

* rm unused

* Update SDK to v0.13.0

* addopt sdk changes

* found better link

* format template

* Update Docs

* Update Gitea SDK (v0.13.1)

* Migrate reactions when migrating repository from github

* fix missed sleep

* fix tests

* update reactions when external user binding

* Fix test

* fix tests

* change the copy head

* fix test

* fix migrator add/delete reaction

* Fix missing updated time on migrated issues and comments

* Fix testing and missing updated on migrating pullrequest

Co-authored-by: Antoine GIRARD <sapk@users.noreply.github.com>

* Store original author info for migrated issues and comments

Keep original author name for displaying in Gitea interface and also
store original author user ID for potential future use in linking
accounts from old location.

* Add original_url for repo

Store the original URL for a migrated repo

Clean up migrations/tests

* fix migration

* fix golangci-lint

* make 'make revive' happy also

* Modify templates to use OriginalAuthor if set

Use the original author name in templates if it is set rather than the
user who migrated/currently owns the issues

* formatting fixes

* make generate-swagger

* Use default avatar for imported comments

* Remove no longer used IgnoreIssueAuthor option

* Add OriginalAuthorID to swagger also

* add migrations

* fix package dependency

* fix lints

* implements migrations except pull requests

* add releases

* migrating releases

* fix bug

* fix lint

* fix migrate releases

* fix tests

* add rollback

* pull request migtations

* fix import

* fix go module vendor

* add tests for upload to gitea

* more migrate options

* fix swagger-check

* fix misspell

* add options on migration UI

* fix log error

* improve UI options on migrating

* add support for username password when migrating from github

* fix tests

* remove comments and fix migrate limitation

* improve error handles

* migrate API will also support migrate milestones/labels/issues/pulls/releases

* fix tests and remove unused codes

* add DownloaderFactory and docs about how to create a new Downloader

* fix misspell

* fix migration docs

* Add hints about migrate options on migration page

* fix tests