The problem: We need to be able to specify configuration in a way that can be inherited to models that include ActiveRecord::Model. So it is no longer sufficient to put 'top level' config on ActiveRecord::Base, but we do want configuration specified on ActiveRecord::Base and descendants to continue to work. So we need something like class_attribute that can be defined on a module but that is inherited when ActiveRecord::Model is included. The solution: added ActiveModel::Configuration module which provides a config_attribute macro. It's a bit specific hence I am not putting this in Active Support or making it a 'public API' at present.
This only existed to support methods like `set_table_name` in Active Record, which are themselves being deprecated.
There's no harm in generating a method name that's already defined on the host class, since we're generating the attribute methods in a module that gets included. In fact, this is desirable as it allows the host class to call super.
This can be overloaded by implementors if necessary.