PHPORM-186 GridFS adapter for Filesystem

[GromNaN]

Fix PHPORM-186

Integration of Flysystem GridFS Adapter for Laravel File Storage.

The configuration is similar to the Symfony Flysystem Bundle as it provides various way to configure the bucket:

• using the database connection (default connection by default)
• setting a service name for the bucket instance
• setting a factory function for the bucket instance

Unlike the Symfony Bundle, I do not provide instantiation of a new MongoDB\Client from the configuration as we always have a database connection with Eloquent.

Checklist

• [x] Add tests and ensure they pass
• [x] Add an entry to the CHANGELOG.md file
• [x] Update documentation for new features

[GromNaN]

LGTM with some comments!

I applied your suggested changes in a new PR: https://github.com/mongodb/laravel-mongodb/pull/2993