User Storage service endpoint for Mini SRCNet Science Platform

The IVOA VOSpace standard provides a REST API for user storage, including use of the IVOA GMS (groups) standard for controlling permissions. The standard provides mechanisms for organising data and moving data to/from a vospace instance by "negotiating" transfer protocols, so it is straightforward to add support for specialised data access/transfer protocols. By default, vospace implementations usually support http(s) transfers, but for science platform integration the client (science platform container) must be able to "mount" the data structure as a (POSIX) file system in one or more containers.

Usage: storing user/project files near the processing resources, storing intermediate and final results, sharing files within the team for further analysis and QA, moving/staging of files in the most appropriate vospace instance for the processing, etc.

architectural note: we expect a distinct vospace service at each SRCNet node and associated with that node's science platform deployment... that means files in there have a globally unique and resolvable identifier as described in the VOSpace standard.

I think this belongs with the deployment story: AC: Demonstrate science platform container file system access to local user storage with file access permissions of the user that launched the container. Demo depends on science platform.