[API, CLI] nodes and interfaces api/command line reference spaces by name and not id

[Michael Foord]

nodes list and interfaces read (command line and equivalent api calls) reference subnet space by name. To use the space (and to reference it internally in juju) we need the id not the name. So we need an extra lookup.

[Michael Foord (mfoord)]

My preference would be adding a space_id field to the json output in addition to the current name.

[Mike Pontillo (mpontillo)]

I'm going to go ahead and close this now, for a few reasons:

 - Spaces can be used by name throughout the MAAS API, including interface constraints. So there's no need to use the ID.

 - Space names are unique in MAAS, and spaces are referenced by name in both MAAS and Juju. The ID isn't particularly meaningful (except to Juju, which is arguably a bug).

 - Juju has been operating without this field for several years now, so this issue doesn't appear to be blocking anyone.