Wrong env file assignment

[vonalbert]

In setup/symfony_server.rst in the "Docker integration" paragraph there's a typo:
the code should be

DATABASE_URL=${MYSQL_URL} instead of MYSQL_URL=${DATABASE_URL}

because you're going to override your local DATABASE_URL value with the autogenerated MYSQL_URL variable provided by the symfony cli tool.

[dbrumann]

I will take a look at it