Issue: Vaultwiki + Amazon S3 (More FILE BB-Code uses)

Originally requested for 3.0.19.

While I like the idea of supporting S3, the attachment storage system overall needs to be made more generic than it already is. So we can use DB storage or file system storage or S3 storage, or write a different storage method, without having to make changes to the original DMs each time.

VaultWiki will use a generic file system in 4.1.x as part of the changes necessary to support XenForo 2.x. So basically it will be possible in VaultWiki 4.1.x to write your own file systems and store attachments there. After re-reading my comment above, I think we can probably improve on this a little more.

Please see how bd attachment store works: https://xenforo.com/community/resour...nt-store.1779/

While XF2 itself still doesn't support remote storage providers out of the box, the storage system in XF2 is built on top of Flysystem which makes adding remote storage providers via add-ons fairly trivial: https://flysystem.thephpleague.com/

Please add support for Digital Ocean Spaces: https://www.digitalocean.com/products/spaces/
This is very cheap file storage and quite popular. $5 for 250GB of storage and 1TB of bandwidth.
API: https://developers.digitalocean.com/...tation/spaces/

Closing this, as the generic storage handler has been implemented in the DMs.