Allow querying multiple namespaces at once

[schmichael]

All HTTP APIs for namespaced objects (eg jobs) only allow querying against a single namespace. They should also support querying multiple namespaces at a time similar to how Policy Namespace Rules can be applied with glob pattern matching: https://learn.hashicorp.com/nomad/acls/policies#namespace-rules

HTTP API Selection, projection, and pagination #7340 could be viewed as a generalization of this issue, but namespacing may warrant special handling given its security implications.

[davejhilton]

+1 this would be incredibly useful.

As you mentioned in terms of "special handling"... obviously there is some trickiness involved here, because it would have to find the intersection of {namespaces matched by the glob} and {namespaces you actually have access to}, so I'm sensitive to the potential complexity of implementing this well. But in our case, this would be incredibly useful, especially for our privileged admins (and some integrations we have that inspect things via the HTTP API)

Additionally, this would be fantastic if it were also extended to the cli as well. It would be great to be able to do things like:
nomad job status -namespace='*-web'
or
nomad job status -namespace='*'

To be honest, my preference might even be to make the default behavior (for the nomad job status cli command especially) be to include things from all namespaces (and add an output column to show the namespace) unless otherwise specified. However I can understand that this would introduce backwards incompatibility issues, and would be a potentially expensive api call for being the default. (I suppose this could also be done just by setting NOMAD_NAMESPACE='*' if globs were supported).

Anyway, figured I'd at least add my input here, as we're evaluating nomad enterprise. Keep up the good work 👍

[tgross]

@schmichael can this one be closed? I know we implemented this for jobs and allocations in 0.12.0 #8192 Was that the limit of what we wanted to do here?

[schmichael]

We're missing /v1/deployments?namespaces=* support

[lgfa29]

CSI plugins and volumes can also benefit from a namespace=* as shown in #11200