Suggestion: `loadFixtures()`: Change the default for `append` to false

The default mode when loading fixtures is to **purge**: https://symfony.com/bundles/DoctrineFixturesBundle/current/index.html#loading-fixtures

> By default the `load` command purges the database

But with `$I->loadFixtures()`, the default is to **append**. I think this is confusing and should be changed. However, I don't see any easy upgrade path... ;-)

Start by locating the implementation and tests for `$I->loadFixtures()` in the module. Compare its current append default with the documented purge behavior, then determine how changing the default affects existing usage and what tests should define the new behavior.

Escrito por el modelo de indexación a partir del texto del issue.