* Fix InsertReleases Nil Insert on Attachments

* FIX "No element on slice when insert" & smal refactor

* again

* impruve

* rm useles newline

* Apply suggestions from code review

Co-Authored-By: zeripath <art27@cantab.net>

* process insert as a whole

Co-authored-by: zeripath <art27@cantab.net>

* Fix bug on upgrade migrated reactions

* Fix migration information update bug when linked github account

Co-authored-by: zeripath <art27@cantab.net>

* fix typo

* Migrate reviews when migrating repository from github

* fix lint

* Added test and migration when external user login

* fix test

* fix commented state

* Some improvements

* fix bug when get pull request and ref original author on code comments

* Fix migrated line; Added comment for review

* Don't load all pull requests attributes

* Fix typo

* wrong change copy head

* fix tests

* fix reactions

* Fix test

* fix fmt

* fix review comment reactions

* 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

* Use batch insert on migrating repository to make the process faster

* fix lint

* fix tests

* fix comments

* 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