After-action change for the standard :assign_* pattern.
Performs an assignment for the named pool via Assigner.assign/3, then
reloads the result via the resource's primary :read action.
Usage
update :assign_port do
argument :assignment, :struct, constraints: [instance_of: Assignment]
change {Diffo.Provider.Changes.Assign, pool: :ports}
endOptions
:pool(required) — the pool name (atom) declared viapools doon the consuming instance resource.