[CDF-24957] Support for 'labels' in Agent resource (#1642)

# Description

When Agents are created through the Agent CRUD API [alpha], they need to
have the (undocumented) property `labels: ['published']`. This PR adds
the ability to add labels to the resource.

## Changelog

- [x] Patch
- [ ] Minor
- [ ] Skip

## cdf

### Added

- [alpha] Agent resource now has `labels` property

## templates

No changes.
