class ActiveSupport::Multibyte::Chars

def normalize(form = nil)

ActiveSupport::Multibyte::Unicode.default_normalization_form
:c, :kc, :d, or :kd. Default is
* form - The form you want to normalize in. Should be one of the following:

and validations.
considered the best normalization form for passing strings to databases
Returns the KC normalization of the string by default. NFKC is 
def normalize(form = nil)
  form ||= Unicode.default_normalization_form
  # See https://www.unicode.org/reports/tr15, Table 1
  if alias_form = Unicode::NORMALIZATION_FORM_ALIASES[form]
    ActiveSupport::Deprecation.warn(<<-MSG.squish)
      ActiveSupport::Multibyte::Chars#normalize is deprecated and will be
      removed from Rails 6.1. Use #unicode_normalize(:#{alias_form}) instead.
    MSG
    send(:unicode_normalize, alias_form)
  else
    ActiveSupport::Deprecation.warn(<<-MSG.squish)
      ActiveSupport::Multibyte::Chars#normalize is deprecated and will be
      removed from Rails 6.1. Use #unicode_normalize instead.
    MSG
    raise ArgumentError, "#{form} is not a valid normalization variant", caller
  end
end