Merge pull request #47222 from rafaelsales/patch-1

Make the purpose of db/seeds.rb clearer through a better description and sample code.

railties/lib/rails/generators/rails/app/templates/db/seeds.rb.tt

@@ -1,7 +1,9 @@
-# This file should contain all the record creation needed to seed the database with its default values.
+# This file should ensure the existence of records required to run the application in every environment (production,
+# development, test). The code here should be idempotent so that it can be executed at any point in every environment.
 # The data can then be loaded with the bin/rails db:seed command (or created alongside the database with db:setup).
 #
-# Examples:
+# Example:
 #
-#   movies = Movie.create([{ name: "Star Wars" }, { name: "Lord of the Rings" }])
-#   Character.create(name: "Luke", movie: movies.first)
+#   ["Action", "Comedy", "Drama", "Horror"].each do |genre_name|
+#     MovieGenre.find_or_create_by!(name: genre_name)
+#   end