Implement bestandsdelen introduced in ZGW Documenten API 1.1 to possibly help with reducing timeouts when uploading large documents when a slow DMS is configured

[MLenterman]

Currently uploading a 256Mb document to OpenZaak takes around 8 sec. It is also possible to configure a DMS as document backend via CMIS in OpenZaak. In this configuration we often see that the DMS is significantly slowing down document uploads to the point where ~40Mb document uploads take 2+ min to complete. Currently it is not realistically possible for municipalities to not use their DMS as document backend, so the only route for performance improvement from our side to change the way documents are uploaded.

Implementing bestandsdelen could potentially help by not having to directly wait for a document upload to finish, as the metadata of the document is added first and the smaller document chunks are uploaded asynchronously afterwards.

• Successfully adding the document metadata with POST enkelvoudigInformatieObject AND successfully writing the document parts to some outbox should be considered a successful upload, despite the document not actually being uploaded yet.
• An outbox pattern(ore something similar) should be used to assure eventual upload of the document parts.
• Uploading of document parts should be done asynchronously and detached from any SOAP-action.