Reproduce rails/activerecord-session_store#116

```
irb(main):001:0> ActiveRecord::Base.belongs_to_required_by_default
=> true
irb(main):002:0> Rails.application.config.active_record.belongs_to_required_by_default
=> false
```

Gemfile

@@ -32,7 +32,7 @@ gem 'jbuilder', '~> 2.5'
 
 # Use Capistrano for deployment
 # gem 'capistrano-rails', group: :development
-
+gem 'activerecord-session_store'
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
   gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]

Gemfile.lock

@@ -33,6 +33,12 @@ GEM
       activemodel (= 5.1.4)
       activesupport (= 5.1.4)
       arel (~> 8.0)
+    activerecord-session_store (1.1.0)
+      actionpack (>= 4.0, < 5.2)
+      activerecord (>= 4.0, < 5.2)
+      multi_json (~> 1.11, >= 1.11.2)
+      rack (>= 1.5.2, < 3)
+      railties (>= 4.0, < 5.2)
     activesupport (5.1.4)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       i18n (~> 0.7)
@@ -178,6 +184,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  activerecord-session_store
   byebug
   capybara (~> 2.13)
   coffee-rails (~> 4.2)
@@ -196,4 +203,4 @@ DEPENDENCIES
   web-console (>= 3.3.0)
 
 BUNDLED WITH
-   1.15.4
+   1.16.0