Consider using extra section instead of config

[JanTvrdik]

• bug report? maybe

The config key is intended to be used by Composer itself, Composer plugins should use the key extra. Using config key does not currently AFAIK cause any issues, but may cause problems in the future.

See https://getcomposer.org/schema.json:

• the config key is described as „Composer options.“
• the extra key is described as „Arbitrary extra data that can be used by plugins, for example, package of type composer-plugin may have a 'class' key defining an installer class name.“

[dg]

I do not know how to get extra data.

[JanTvrdik]

Looking at Composer repo it looks like $event->getComposer()->getPackage()->getExtra() should work.