Map the app entities by default

[qzminski]

Description The Doctrine entities inside App namespace could probably be mapped by default. This requires some changes in the current config skeleton: https://github.com/contao/contao/blob/master/manager-bundle/src/Resources/skeleton/config/config.yml#L54

Example As of now I have to provide this configuration on my own:

doctrine:
    orm:
        mappings:
            App:
                type: annotation
                dir: '%kernel.project_dir%/src/Entity'
                is_bundle: false
                prefix: App\Entity
                alias: App

/cc @aschempp

[m-vo]

I've put that in every project as well. Not sure if the Entity directory needs to exist for this to work.

[leofeyer]

As discussed in Mumble on August 27th, we cannot add this into the config.yml, because it will fail if there is no Entity folder. However, we could add a compiler pass that checks the existing configuration and dynamically adds the mapping if the Entity folder exists.

[Toflar]

I don't think we can do this. See https://github.com/symfony/doctrine-bridge/blob/4e6cfe4c9a1e6e3b7ff8f1e0e0996bf138ee1205/DependencyInjection/AbstractDoctrineExtension.php#L226

[aschempp]

see #2232