Source: https://www.levups.com/en/blog/2017/undocumented-dirty-attributes-activerecord-changes-rails51.html

Using the <attribute>_changed? helper along saved_change_to_<attribute> is now more comprehensible:
```ruby
user = User.last
user.name                   # => "Bob"
user.name_changed?          # => false
user.saved_change_to_name?  # => false

user.name = "Clément"       # => "Clément"
user.name_changed?          # => true
user.saved_change_to_name?  # => false

user.save                   # => true

user.name                   # => "Clément"
user.name_changed?          # => false
user.saved_change_to_name?  # => true
```