Creating an upgrade schema script (UpgradeSchema.php)

During the first-time module install, an upgrade schema is what gets run immediately after an install schema. We define upgrade schema within the app/code/Foggyline/Office/Setup/UpgradeSchema.php file with (partial) content as follows:

namespace Foggyline\Office\Setup;

use Magento\Framework\Setup\UpgradeSchemaInterface;
use Magento\Framework\Setup\ModuleContextInterface;
use Magento\Framework\Setup\SchemaSetupInterface;

class UpgradeSchema implements UpgradeSchemaInterface
{
    public function upgrade(SchemaSetupInterface $setup, ModuleContextInterface $context)
    {
        $setup->startSetup();
          /* #snippet1 */
        $setup->endSetup();
    }
}

UpgradeSchema conforms to UpgradeSchemaInterface, which requires the implementation of the upgrade method that accepts two parameters of type SchemaSetupInterface and ModuleContextInterface.

This is quite similar to InstallSchemaInterface, except the method name. The update...