5.1.5

This patch level release has the following bug fixes:

• MONGOID-4315 Eager load objects when criteria docs are enumerated multiple times
• MONGOID-4350 Fix counter_cache update when foreign_key isn't default (@TheSmartnik)
• MONGOID-4313, MONGOID-4317 Fix Includes throwing NoMethodError when document is nil
• MONGOID-3407 Fix setting a hash field with atomic operator
• Use right database when override_database + options. (@sylvain-8422)