fix decomposedfs upload

[butonic]

The FS.Upload() implementation needs to handle direct uploads that did not initiate a unpload.

fixes ocis spaces registry PR owncloud/ocis#2739

ocis makes direct PUT /data/spaces/spaceid!spaceid/relative/path/to/file.json requests to the metadata storage data provider. No initiate upload call ... we did that to save requests. Might be better to just use TUS with the creation-with-upload extension.

For now this allows us to create users with ocis and the accounts service.

[wkloucek]

This is completely against the CS3api spec... It will create hidden complexity and produce bugs like owncloud/ocis#2609. That's why we removed zero-byte-uploads and the functionality you just added again in #2309.

Can we please revert this and solve it properly?

CC @C0rby

[butonic]

I agree the different upload mechanisms currently are confusing:

• we have the InitiateFileUpload call which returns a "simple" or "tus" protocol endpoint
• both protocols take an upload id, but
  • the eos driver uses a path as the upload token
  • the ocis metadata service bypasses all this as it used the "simple" protocol with a path

We should fix the metadata service to make the proper InitiateFileUpload + PUT request. While this will create more requests we can improve that later, similar to the creation-with-upload extension of TUS.