Accept any Que::Adapters::Base subclass in Que.connection=

Replace the hardcoded class-name whitelist with an is_a?(Adapters::Base)
guard, so external adapter subclasses (e.g. defined in consuming apps) can
be passed directly without raising "Que connection not recognized".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: BBrannick

lib/que.rb

@@ -62,9 +62,10 @@ def connection=(connection)
       self.adapter =
         if connection.to_s == "ActiveRecord"
           Adapters::ActiveRecord.new
+        elsif connection.is_a?(Adapters::Base)
+          connection
         else
           case connection.class.to_s
-          when "Que::Adapters::ActiveRecordWithLock" then connection
           when "Sequel::Postgres::Database" then Adapters::Sequel.new(connection)
           when "ConnectionPool"             then Adapters::ConnectionPool.new(connection)
           when "PG::Connection"             then Adapters::PG.new(connection)

spec/lib/que/que_spec.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+RSpec.describe Que do
+  describe ".connection=" do
+    it "accepts a custom Adapters::Base subclass instance and sets it as the adapter" do
+      custom_adapter_class = Class.new(Que::Adapters::Base)
+      stub_const("MyApp::CustomAdapter", custom_adapter_class)
+      custom_adapter = MyApp::CustomAdapter.new
+
+      expect { Que.connection = custom_adapter }.not_to raise_error
+      expect(Que.adapter).to eq(custom_adapter)
+    end
+
+    it "raises for an unrecognized non-adapter object" do
+      expect { Que.connection = Object.new }.
+        to raise_error(/Que connection not recognized/)
+    end
+  end
+end