Staged Deployments (Release Streams)

[nshoes]

In #1652, we changed how we pull a device from deployment on connect. In the old-world, we'd check that the firmware version on device.firmware_metadata matched the associated deployment's version requirements.

# deployment_one
- version requirement: <1.0.0
- firmware version: 1.0.0

# deployment_two
- version requirement: 1.0.0
- firmware version: 1.0.1

This essentially allowed staged deployments. Once a device upgrade succeeded in deployment_one it would reconnect and be placed in deployment_two. In the new-world, we only check architecture and platform so this workflow isn't possible.

This feature lines up neatly with #1653. We could allow the user to pick a set of version and firmware requirements for a DeploymentGroup and then handle the rest.

# deployment_group.ex
has_many :deployment_stages
field :staged, :boolean, default: false

# deployment_stage.ex
belongs_to :deployment_group
field :version_requirement, :string
field :firmware_id
field :archive_id

There's more to figure out but I'm going to be rough on the specifics for now; I'm just jotting this down before I talk with others.