How to enable a module via code - Drupal 8/9

There are very rare occasions where you might need to enable modules via a hook_update instead of through a config import.

In order to do this, you would have to create a `.install` file within your custom module and use the hook_update_N hook.

For example, the following code will enable all the modules when `drush updb` is executed.

/**
 * Enable a few modules
 */
function MY_MODULE_NAME_update_9001() {
  $modules = ['webform', 'config_ignore', 'devel'];

  foreach ($modules as $module) {
    // we want to make sure these modules are not already enabled.
    if (!\Drupal::moduleHandler()->moduleExists($module)) {
      \Drupal::service('module_installer')->install([$module]);
    }
  }
}