enable archive download by resourceid

[butonic]

As a follow-up of cs3org/reva#2066
The current implementation only handles path based requests.

For the spaces concept we need to be able to download archives that contain a list of resource ids.

[jvillafanez]

I guess the question here is, who's going to convert the resource id to a path?

So far, ocis is mostly routing the request to the archiver service. As such, converting the resource id to a path doesn't seem possible in ocis unless we change the approach.

The alternative is that the archiver handles the resource id by itself, converting it to a path if needed. In this case, ocis shouldn't need any change, but reva.

[butonic]

The case I have in mind is when the resourceid comes from a PROPFIND /dav/spaces/<spaceid></optional/relative/path>. The references we give to the archiver are opaque to it. It only needs to fetch the resources using references that contain the spaceid and the path. They were introduced with cs3org/reva#1721 and are used whenever accessing a storage space. They can also transport plain paths, so it should be possible to extend the axisting /archive implementation with relative references.

[wkloucek]

Will be fixed by cs3org/reva#2100

[kulmann]

Linked PR is merged, archive download by base64 encoded resourceid now works. Closing here.