Adds dump_all_fixtures and dump_fixture to ApplicationRecord

dump_fixtures.rb

class ApplicationRecord < ActiveRecord::Base
# ...
  def self.dump_all_fixtures
    self.all.map(&:dump_fixture)
  end

  def dump_fixture
    fixture_file = "#{Rails.root}/spec/fixtures/#{self.class.table_name}.yml"
    File.open(fixture_file, "a+") do |f|
      f.puts({ "#{self.class.table_name.singularize}_#{id}" => attributes.reject{|key| %w(id created_at updated_at).include?(key)} }.
        to_yaml.sub!(/---\s?/, "\n"))
    end
  end
# ...
end

# https://stackoverflow.com/questions/6591722/how-to-generate-fixtures-based-on-my-development-database
# https://stackoverflow.com/questions/49234751/how-to-read-ruby-object-in-yaml