Works on MySQL only

Problem/Motivation

After installing on a PostgreSQL-based site, an exception is thrown:

TypeError: Argument 1 passed to Drupal\unmanaged_files\UnmanagedFilesManager::__construct() must be an instance of Drupal\Core\Database\Driver\mysql\Connection, instance of Drupal\Core\Database\Driver\pgsql\Connection given

Steps to reproduce

1. Install the module on a PostgreSQL-based site
2. Navigate to /admin/config/media/unmanaged-files
3. The above exception is thrown.

Proposed resolution

Type-hint the relevant argument in UnmanagedFilesManager::__construct() to Drupal\Core\Database\Connection instead of Drupal\Core\Database\Driver\mysql\Connection.

Remaining tasks

User interface changes

API changes

Data model changes