Restore AR 5.x/6.x compatibility in default_timezone and spec_helper

Commit 3d84e73 migrated default_timezone to the module-level
ActiveRecord.default_timezone API, which only exists on AR 7.0+.
Commit a37d58a then added a CI matrix covering AR 5.0-6.1, exposing
two latent failures:

- AR 5.0/5.1/5.2 raise NoMethodError on ActiveRecord.default_timezone=
- AR 6.0/6.1 fail to load active_record with
  "uninitialized constant ActiveSupport::LoggerThreadSafeLevel::Logger"
  because logger is not required before active_support.

Version-gate the default_timezone accessor in both lib/plsql/schema.rb
and spec/plsql/schema_spec.rb via ActiveRecord.respond_to?, and require
"logger" before "active_record" in spec/spec_helper.rb.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: yahonda

lib/plsql/schema.rb

@@ -100,7 +100,8 @@ def default_timezone
       else
         @default_timezone ||
           # Use ActiveRecord default_timezone when ActiveRecord connection is used
-          (@connection && @connection.activerecord_class && ActiveRecord.default_timezone) ||
+          (@connection && @connection.activerecord_class &&
+            (ActiveRecord.respond_to?(:default_timezone) ? ActiveRecord.default_timezone : ActiveRecord::Base.default_timezone)) ||
           # default to local timezone
           :local
       end

spec/plsql/schema_spec.rb

@@ -209,8 +209,12 @@ class TestModel < TestBaseModel
     expect(plsql.schema_name).to eq("HR")
   end
 
-  it "should use ActiveRecord.default_timezone as default" do
-    ActiveRecord.default_timezone = :utc
+  it "should use ActiveRecord default_timezone as default" do
+    if ActiveRecord.respond_to?(:default_timezone=)
+      ActiveRecord.default_timezone = :utc
+    else
+      ActiveRecord::Base.default_timezone = :utc
+    end
     expect(plsql.default_timezone).to eq(:utc)
   end
 

spec/spec_helper.rb

@@ -19,6 +19,7 @@
 require "rspec"
 
 unless ENV["NO_ACTIVERECORD"]
+  require "logger"
   require "active_record"
   require "active_record/connection_adapters/oracle_enhanced_adapter"
   if ActiveRecord::ConnectionAdapters.respond_to?(:register)