Move migrating repository from frontend to backend (#6200)

* move migrating to backend

* add loading image when migrating and fix tests

* fix format

* fix lint

* add redis task queue support and improve docs

* add redis vendor

* fix vet

* add database migrations and fix app.ini sample

* add comments for task section on app.ini.sample

* Update models/migrations/v84.go

Co-Authored-By: lunny <xiaolunwen@gmail.com>

* Update models/repo.go

Co-Authored-By: lunny <xiaolunwen@gmail.com>

* move migrating to backend

* add loading image when migrating and fix tests

* fix fmt

* add redis task queue support and improve docs

* fix fixtures

* fix fixtures

* fix duplicate function on index.js

* fix tests

* rename repository statuses

* check if repository is being create when SSH request

* fix lint

* fix template

* some improvements

* fix template

* unified migrate options

* fix lint

* fix loading page

* refactor

* When gitea restart, don't restart the running tasks because we may have servel gitea instances, that may break the migration

* fix js

* Update models/repo.go

Co-Authored-By: guillep2k <18600385+guillep2k@users.noreply.github.com>

* Update docs/content/doc/advanced/config-cheat-sheet.en-us.md

Co-Authored-By: guillep2k <18600385+guillep2k@users.noreply.github.com>

* fix tests

* rename ErrTaskIsNotExist to ErrTaskDoesNotExist

* delete release after add one on tests to make it run happy

* fix tests

* fix tests

* improve codes

* fix lint

* fix lint

* fix migrations

options/locale/locale_en-US.ini

@@ -633,6 +633,8 @@ migrate.lfs_mirror_unsupported = Mirroring LFS objects is not supported - use 'g
 migrate.migrate_items_options = When migrating from github, input a username and migration options will be displayed.
 migrated_from = Migrated from <a href="%[1]s">%[2]s</a>
 migrated_from_fake = Migrated From %[1]s
+migrate.migrating = Migrating from <b>%s</b> ...
+migrate.migrating_failed = Migrating from <b>%s</b> failed.
 
 mirror_from = mirror of
 forked_from = forked from