copy_attribute_definitions uses type_for_attribute, fallback_to_model_values checks against original_attributes_hash

[tcannonfodder]

copy_attribute_definitions uses type_for_attribute

• Using type_for_attribute seems to handle mapping certain ActiveRecord columns to ActiveModel types, notably TEXT => string in the example application
  • Unfortunately, we still need to use the columns_hash to pull the default value from the column's definition

fallback_to_model_values checks against original_attributes_hash

• When an attribute has a default value, the check for if the attribute is falsey will be false, since it's using the default value
  • Instead, we want to actually check against the original_attributes_hash (the user-provided hash of attributes, such as the one used by initialize) to see if it had a value for that key
    • If so, we assume that the value has already been processed and does not need the fallback applied
• Updated the tests to verify this behavior by setting a default for the body column and checking that
  • An empty model instance is initialized with the default
  • The model's fallback value is loaded if there was no value provided when initializing