Discourse 从 2.7.0.beta8 版本开始使用 ActiveRecord 6.1.3.1，在此之前使用的是 ActiveRecord 6.0.3.5。这都没什么问题，但 Discourse Plugin Linkedin Auth (20211203171247_migrate_linkedin_user_info.rb) 中添加了一个迁移，可能是在 2021-12-03 添加的，这在尝试重建时会导致此错误：
Caused by:
ArgumentError: Unknown migration version "6.1"; expected one of "4.2", "5.0", "5.1", "5.2", "6.0"
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration/compatibility.rb:11:in `find'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:544:in `[]'
/var/www/discourse/plugins/discourse-plugin-linkedin-auth/db/migrate/20211203171247_migrate_linkedin_user_info.rb:3:in `<main>'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `require'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:23:in `block in require_with_bootsnap_lfi'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require_with_bootsnap_lfi'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/bootsnap-1.7.2/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:31:in `require'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/zeitwerk-2.4.2/lib/zeitwerk/kernel.rb:34:in `require'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1010:in `load_migration'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1006:in `migration'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1002:in `disable_ddl_transaction'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1368:in `use_transaction?'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1360:in `ddl_transaction'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1309:in `execute_migration_in_transaction'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1281:in `block in migrate_without_lock'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1280:in `each'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1280:in `migrate_without_lock'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1229:in `block in migrate'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1382:in `with_advisory_lock'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1229:in `migrate'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1061:in `up'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/migration.rb:1036:in `migrate'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/activerecord-6.0.3.5/lib/active_record/tasks/database_tasks.rb:238:in `migrate'
/var/www/discourse/lib/tasks/db.rake:215:in `block in <main>'
/var/www/discourse/vendor/bundle/ruby/2.7.0/gems/rake-13.0.3/exe/rake:27:in `<top (required)>'
/usr/local/bin/bundle:23:in `load'
/usr/local/bin/bundle:23:in `<main>'
Tasks: TOP => db:migrate
我在插件中找不到任何分支可以让我安装旧版本，因此我必须在旧的 Discourse 版本上禁用该插件。
（注意，我们确实打算升级到 2.7.0；我们只是想克隆我们现有的（旧的）Discourse，但由于插件迁移失败而无法做到。）
谢谢。