Add functional tests

src/Builder/CapsuleBuilder.php

src/Controller/CapsuleController.php

src/Controller/CapsuleEditorController.php

src/DataFixtures/CapsuleFixtures.php

src/Entity/CapsuleEditor.php

src/Repository/CapsuleEditorRepository.php

templates/capsule/editors/email_editor.html.twig

tests/functional/CapsuleControllerTest.php

tests/functional/CapsuleEditorControllerTest.php