Dunglas\Heroku\Database not on autorun

When deploying I was not able to put that class on autorun. I did it locally by running composer update. But was not able to do it on heroku.

So I decided to use this that seemed a better approach than having to rely on that Database::createParameters method:

```
doctrine:
dbal:
driver: pdo_mysql
url: "%env(DATABASE_URL)%"
```

Start at the Dunglas\Heroku\Database class and the deployment or autoload configuration used by the Symfony application; compare the failing Heroku deployment with the composer update behavior described here. Done means the class is available through the intended autorun path on Heroku, with the shown DATABASE_URL Doctrine configuration remaining verifiable.

Written by the indexing model from the issue text.