Add Rails 7.1 compatibility (partial - 664/674 tests passing)

Implement Rails 7.1 compatibility fixes while maintaining backward
compatibility with Rails 6.1 and 7.0:

Changes:
- Fix version-conditional app initialization in test_helper.rb
  - Rails 7.1+ requires TestApp.initialize! before rails/test_help
  - Rails 6.1/7.0 require opposite order
- Fix schema compatibility in active_record.rb
  - Change t.string :length option to :limit (Rails 7.1 deprecation)
  - Change t.references :references option to foreign_key: false
- Disable SQLite foreign key constraints in test environment
  - Rails 7.1 enables strict FK constraints by default
  - Added PRAGMA foreign_keys = OFF for test compatibility

Backward compatibility verified:
- Rails 6.1.7.10: ✅ 674/674 tests passing
- Rails 7.0.10: ✅ 674/674 tests passing

Rails 7.1.6 status:
- 664/674 tests passing (98.5%)
- 1 failure: RequestTest expecting 422, got 0
- 9 errors: "Invalid response code: 0" in controller tests

Remaining work:
- Investigate and fix response code 0 errors
- Get all 674 tests passing in Rails 7.1.6

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: takaokouji

test/fixtures/active_record.rb

@@ -52,7 +52,7 @@
   end
 
   create_table :posts, force: true do |t|
-    t.string     :title, length: 255
+    t.string     :title, limit: 255
     t.text       :body
     t.integer    :author_id
     t.integer    :parent_post_id
@@ -324,8 +324,8 @@
 
   create_table :related_things, force: true  do |t|
     t.string :name
-    t.references :from, references: :thing
-    t.references :to, references: :thing
+    t.references :from, foreign_key: false
+    t.references :to, foreign_key: false
 
     t.timestamps null: false
   end

test/test_db-shm

@@ -47,29 +47,10 @@
 ENV['DATABASE_URL'] ||= "sqlite3:test_db"
 
 require 'active_record/railtie'
-require 'rails/test_help'
-require 'minitest/mock'
-require 'jsonapi-resources'
-require 'pry'
-
-require File.expand_path('../helpers/value_matchers', __FILE__)
-require File.expand_path('../helpers/assertions', __FILE__)
-require File.expand_path('../helpers/functional_helpers', __FILE__)
-require File.expand_path('../helpers/configuration_helpers', __FILE__)
 
+# Rails 7.1+ requires the application to be defined before requiring rails/test_help
 Rails.env = 'test'
 
-I18n.load_path += Dir[File.expand_path("../../locales/*.yml", __FILE__)]
-I18n.enforce_available_locales = false
-
-JSONAPI.configure do |config|
-  config.json_key_format = :camelized_key
-end
-
-ActiveSupport::Deprecation.silenced = true
-
-puts "Testing With RAILS VERSION #{Rails.version}"
-
 class TestApp < Rails::Application
   config.eager_load = false
   config.root = File.dirname(__FILE__)
@@ -91,6 +72,39 @@ class TestApp < Rails::Application
   end
 end
 
+# Rails 7.1+ requires the application to be initialized before requiring rails/test_help
+# Earlier versions require the opposite order
+if Rails::VERSION::MAJOR >= 8 || (Rails::VERSION::MAJOR == 7 && Rails::VERSION::MINOR >= 1)
+  TestApp.initialize!
+end
+
+require 'rails/test_help'
+
+# Initialize app for Rails < 7.1 (for Rails 7.1+ it was already initialized above)
+unless Rails::VERSION::MAJOR >= 8 || (Rails::VERSION::MAJOR == 7 && Rails::VERSION::MINOR >= 1)
+  TestApp.initialize!
+end
+
+require 'minitest/mock'
+require 'jsonapi-resources'
+require 'pry'
+
+require File.expand_path('../helpers/value_matchers', __FILE__)
+require File.expand_path('../helpers/assertions', __FILE__)
+require File.expand_path('../helpers/functional_helpers', __FILE__)
+require File.expand_path('../helpers/configuration_helpers', __FILE__)
+
+I18n.load_path += Dir[File.expand_path("../../locales/*.yml", __FILE__)]
+I18n.enforce_available_locales = false
+
+JSONAPI.configure do |config|
+  config.json_key_format = :camelized_key
+end
+
+ActiveSupport::Deprecation.silenced = true
+
+puts "Testing With RAILS VERSION #{Rails.version}"
+
 DatabaseCleaner.allow_remote_database_url = true
 DatabaseCleaner.strategy = :transaction
 
@@ -214,10 +228,15 @@ def show_queries
   end
 end
 
-TestApp.initialize!
+# TestApp.initialize! already called earlier for Rails 7.1+ compatibility
 
 require File.expand_path('../fixtures/active_record', __FILE__)
 
+# Disable foreign key constraints for SQLite in test environment (Rails 7.1+)
+# This allows force: true to drop and recreate tables without constraint errors
+# Must be called after active_record.rb which sets up the schema
+ActiveRecord::Base.connection.execute("PRAGMA foreign_keys = OFF") if ActiveRecord::Base.connection.adapter_name == 'SQLite'
+
 module Pets
   module V1
     class CatsController < JSONAPI::ResourceController