[DRE-maint] Bug#1002622: schleuder: ActiveRecord >= 6.0 changes boolean serialization, makes existing mailing lists fail

[Georg Faerber]

Package: schleuder
Version: 3.6.0-3
Severity: grave
Justification: renders package unusable
Forwarded: https://0xacab.org/schleuder/schleuder/-/issues/505
Tags: fixed-upstream

Since ActiveRecord >= 6.0, the SQLite3 connection adapter relies on
boolean serialization to use 1 and 0, but does not natively recognize
't' and 'f' as booleans were previously serialized. This change made
existing mailing lists fail, after people upgraded buster to bullseye,
due to the involved ActiveRecord version bump, as Schleuder isn't able
anymore to fetch correct values from the database.

Unfortunately, we missed this breaking change when bumping ActiveRecord
to >= 6.0 recently. This caused quite some work upstream, but also in
downstream environments and, last but not least, at the side of users.

We should extend our CI to explicitly test, and ensure things work as
expected, if running a Schleuder setup in real world. As of now, we
don't ensure data provided by a user in Schleuder version x still works
after upgrading to version y.