Context: How is the app/etc/config.php file generated by the \Magento\Setup\Model\Installer::createModulesConfig()?
app/etc/config.php
\Magento\Setup\Model\Installer::createModulesConfig()
Details: How does \Magento\Framework\App\DeploymentConfig::load() work?
\Magento\Framework\App\DeploymentConfig::load()
See also:
app/etc/env.php