feat(cli): add delete-users-by-role command

[kariae]

Add delete-users-by-role command

This PR introduces a new WP-CLI command delete-users-by-role that allows for bulk deletion of WordPress users based on their roles.

Features

• Delete users by specifying roles to delete:

  wp newspack-migration-tools delete-users-by-role --roles=subscriber,author

• Delete users by excluding specific roles:

  wp newspack-migration-tools delete-users-by-role --exclude-roles=administrator,editor

• Optional post reassignment:

  wp newspack-migration-tools delete-users-by-role --roles=subscriber --reassign-to=1

• Dry-run mode for safety:

  wp newspack-migration-tools delete-users-by-role --roles=subscriber --dry-run

Implementation Details

• Validates roles before processing
• Handles post reassignment/deletion
• Includes detailed logging
• Includes comprehensive test suite
• Includes workaround for Co-Authors Plus issue #1096

Testing Instructions

1. Install and activate the plugin
2. Run the command with --dry-run to preview changes:

   wp newspack-migration-tools delete-users-by-role --roles=subscriber --dry-run

3. Run without --dry-run to perform actual deletion
4. Test with both --roles and --exclude-roles parameters
5. Test with and without --reassign-to parameter

QA Checklist

• Code follows WordPress coding standards
• All tests pass
• Documentation is clear and complete
• Command handles edge cases gracefully