Use model.arel_table in ActiveRecord get_all for Rails main compatibility

[kylekeesling]

Problem

Flipper::Adapters::ActiveRecord#get_all builds its join query with positional Arel::Table.new calls:

features = ::Arel::Table.new(@feature_class.table_name.to_sym)
gates    = ::Arel::Table.new(@gate_class.table_name.to_sym)

Rails main reworked Arel::Table to be keyword-only (rails/rails#57021 — def initialize(name: nil, as: nil, klass: nil, ...)). The positional call now raises:

ArgumentError: wrong number of arguments (given 1, expected 0)

Because Flipper::Middleware::Memoizer calls preload_all → get_all on every request, this breaks every request (including health-check endpoints) on any app tracking Rails main / edge. We hit this in production when our Rails-main pin moved past that commit.

Fix

Use ActiveRecord::Base.arel_table instead. It returns the same table, is maintained by Rails, and has existed since Rails 4 — so it sidesteps the constructor signature entirely and works across the full supported matrix (5.2–8.0) and Rails main.

features = @feature_class.arel_table
gates    = @gate_class.arel_table

Testing

• bundle exec rspec spec/flipper/adapters/active_record_spec.rb (sqlite): 52 examples, 0 failures (the 2 pending are pre-existing sqlite role limitations).
• Verified downstream against Rails main: reproduced the ArgumentError, confirmed the change makes Flipper.preload_all succeed.

CI's matrix doesn't currently include Rails main, so this regression isn't caught upstream — happy to add a rails: main matrix entry in a follow-up if useful.