def file_field_options(method, custom_options)
      default_file_field_options(method).merge(custom_options) do |_key, default, custom|
        default.is_a?(Hash) && custom.is_a?(Hash) ? default.merge(custom) : custom
      end
    end
def file_field_options(method, custom_options)
      default_file_field_options(method).merge(custom_options) do |_key, default, custom|
        default.is_a?(Hash) && custom.is_a?(Hash) ? default.merge(custom) : custom
      end
    end
Merges the user provided options with the default options overwriting the defaults to
 generate the final options passed to the embedded file input field.

 @author Ian Grant
 @param [Symbol] method The attribute on the target model to attach the files to.
 @param [Hash] custom_options The user provided custom options hash.
 @return [Hash] The user provided options and default options merged.