def first_name=(first_name)
      name = Name.new(first_name, 'Last')
      raise "invalid first name" unless name.first.length > 0
      @first_name = name.first
    end
def first_name=(first_name)
      name = Name.new(first_name, 'Last')
      raise "invalid first name" unless name.first.length > 0
      @first_name = name.first
    end
Constructor. Must supply both names and a unique number for the tournament.
 Canonicalise and set the first name(s).