Fix ActiveRecord 8.0 default_timezone API and add debug-frozen-string-literal

ActiveRecord 8.0 removed ActiveRecord::Base.default_timezone= in
favor of ActiveRecord.default_timezone. Update both the library code
and spec.

Also add --debug-frozen-string-literal to help identify frozen string
literal warnings.

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

Author: yahonda

.github/workflows/test.yml

@@ -84,4 +84,4 @@ jobs:
         bundle install --jobs 4 --retry 3
     - name: Run RSpec
       run: |
-        RUBYOPT=-w bundle exec rspec
+        RUBYOPT="-w --debug-frozen-string-literal" bundle exec rspec

.github/workflows/test_11g.yml

@@ -85,4 +85,4 @@ jobs:
         bundle install --jobs 4 --retry 3
     - name: Run RSpec
       run: |
-        RUBYOPT=-w bundle exec rspec
+        RUBYOPT="-w --debug-frozen-string-literal" bundle exec rspec

lib/plsql/schema.rb

@@ -99,8 +99,8 @@ def default_timezone
         @original_schema.default_timezone
       else
         @default_timezone ||
-          # Use ActiveRecord class default_timezone when ActiveRecord connection is used
-          (@connection && (ar_class = @connection.activerecord_class) && ar_class.default_timezone) ||
+          # Use ActiveRecord default_timezone when ActiveRecord connection is used
+          (@connection && @connection.activerecord_class && ActiveRecord.default_timezone) ||
           # default to local timezone
           :local
       end

spec/plsql/schema_spec.rb

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