Sample debug app

Related to PR : symfony/symfony#40856

git clone [email protected]:monteiro/PR-40856.git
composer install
// up the postgresql db
docker-compose up
bin/console doctrine:migrations:migrate
bin/console doctrine:fixtures:load
symfony serve

execute curl localhost:8000/api/contacts
- you should see a JSON of contacts with 2 fields
go to src/Entity/Contact.php and add or remove @Groups("contacts_get") on the entity properties, save
execute curl localhost:8080/api/contacts
- ⚠️ you should see no changes
execute cache:clear
execute curl localhost:8080/api/contacts
- ⚠️ you should see changes

Notes: This issue was reported by @jhice