[DRE-maint] Bug#968971: gitlab: Can't create new project: undefined method `set_attribute_was'

[Antoine Le Gonidec]

Here I am running 13.2.8-1+fto10+2 on top of a Debian Buster, following the recommended "FastTrack" installation method.

I get a similar error related to a missing "set_attribute_was" method when trying to add a new push mirror to an existing repository.

The only mentions I found of this method are in the following packages:
- ruby-acts-as-taggable-on: /usr/lib/ruby/vendor_ruby/acts_as_taggable_on/taggable/core.rb
- ruby-attr-encrypted: /usr/lib/ruby/vendor_ruby/attr_encrypted/adapters/active_record.rb

Both are installed from Buster backports:
- ruby-acts-as-taggable-on: 6.5.0-2~bpo10+1
- ruby-attr-encrypted: 3.1.0-2~bpo10+1

The method "set_attribute_was" used to be provided by ruby-activemodel in its 5.* version (Buster and official Buster backports), but is not part of the 6.* version (FastTrack-provided backports).

If I remove the calls to "set_attribute_was" from the two listed .rb files and restart the gitlab service, I no longer get the crash on addition of a new push mirror. I attached the edited source files to this e-mail for testing purposes, but keep in mind that I am not a Ruby developer, I only removed some part of the scripts without worrying about the consequences. If you use these edited files without a careful review, things are expected to break in unexpected ways ;)
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