Move the `ActiveModel:Errors#full_message` method to the `Error` class:

- One regression introduced by the "AM errors as object" features is
  about the `full_messages` method.

  It's currently impossible to call that method if the `base` object
  passed in the constructor of `AM::Errors` doesn't respond to the
  `errors` method.
  That's because `full_messages` now makes a weird back and forth trip

  `AM::Errors#full_messages` -> `AM::Error#full_message` -> `AM::Errors#full_message`

  Since `full_message` (singular) isn't needed by AM::Errors, I moved
  it to the `AM::Error` (singular) class. This way we don't need to
  grab the `AM::Errors` object from the base.

1 files changed, 1 insertions, 1 deletions

diff --git a/activemodel/lib/active_model/railtie.rb b/activemodel/lib/active_model/railtie.rb
index eb7901c7e9..65e20b9791 100644
--- a/activemodel/lib/active_model/railtie.rb
+++ b/activemodel/lib/active_model/railtie.rb
@@ -14,7 +14,7 @@ module ActiveModel
     end
 
     initializer "active_model.i18n_customize_full_message" do
-      ActiveModel::Errors.i18n_customize_full_message = config.active_model.delete(:i18n_customize_full_message) || false
+      ActiveModel::Error.i18n_customize_full_message = config.active_model.delete(:i18n_customize_full_message) || false
     end
   end
 end