Add support for core config installer

[neclimdul]

Description

Thanks to https://www.drupal.org/project/drupal/issues/2788777 and https://www.drupal.org/project/drupal/issues/2980670 core now supports installing directly from config without the need of a profile. This doesn't just happen out of the box, there is a new config_install_path parameter in install_state that toggles a lot of behaviors in the installer.

To support installing from config in Drush, SiteInstallCommands will need to be updated to support providing this.

Goal

To supporting installing from config directly in Drush.

[neclimdul]

open source rocks. already a pull request!

I poked at this a little too and there are actually 2 ways to trigger the behavior. The pull request is the most explicit but you can also have the installer use the default directory with a different parameter.

Seems like its worth supporting both so I'll look at pulling together a pull request.

Trivial POC patch looked like this:

diff --git a/src/Commands/core/SiteInstallCommands.php b/src/Commands/core/SiteInstallCommands.php
index 615979b6..06962834 100644
--- a/src/Commands/core/SiteInstallCommands.php
+++ b/src/Commands/core/SiteInstallCommands.php
@@ -81,6 +81,7 @@ class SiteInstallCommands extends DrushCommands implements SiteAliasManagerAware
             'parameters' => [
                 'profile' => $profile,
                 'langcode' => $options['locale'],
+                'existing_config' => TRUE,
             ],
             'forms' => [
                 'install_settings_form' => [

[vpeltot]

@neclimdul I have added the --existing-config option to allow the installation from the config sync directory.
Please see the PR #3625

[weitzman]

Lets discuss in PR