Webform delete and removal of files

I moved this to the feature branch.

Config import command output:

// Import the listed configuration changes?: yes.                              

 [error]  Access denied to file at uri location://webform/webform_name
 [warning] Unable to remove webform files from location://webform/webform_name. Message 
 [notice] Synchronized configuration: delete webform.webform.webform_name.
 [notice] Finalizing configuration synchronization.
 [success] The configuration was imported successfully.

The private:// file system requires authentication, so we can use it for testing.

All submissions have to be deleted before a webform is deleted via config-import. See the below steps.

I am unsure what triggers the error for your authenticated file system. It is very possible that this error is specific to your file system.

One guess is via Drush, you will need to use an authenticated user during the config import. This does not seem to be supported.
@see 📌 Run drush imports as user=1 RTBC

Steps attempting to replicate

• Import or create the attached webform. /admin/config/development/configuration/single/import
• Add test results to the new webform. /webform/issue_3359937/test
• Export config. `drush config-export`
• Duplicate the webform. /admin/structure/webform/manage/issue_3359937/duplicate
• Add test results to the duplicate webform. /webform/issue_3359937_duplicate/test
• Import config and config delete duplicate webform. `drush config-import`
• Confirm that 'These entities need to be deleted before importing.' is displayed.
• Delete all duplicate submissions. /admin/structure/webform/manage/issue_3359937_duplicate/results/clear
• Import config and config delete duplicate webform. `drush config-import`
• Confirm that the duplicate webform is deleted.