feat: kadabra, the app auto-updater (!268)

coop-cloud/organising#236

Autoupdater `kadabra` is ready for testing.
It should run on the server, check for available minor/patch updates and automatically upgrade the apps.

Co-authored-by: Moritz <moritz.m@local-it.org>
Reviewed-on: coop-cloud/abra#268

pkg/upstream/stack/stack.go

@@ -10,6 +10,7 @@ import (
 
 	"coopcloud.tech/abra/pkg/upstream/convert"
 	"github.com/docker/cli/cli/command/service/progress"
+	"github.com/docker/cli/cli/command/stack/formatter"
 	composetypes "github.com/docker/cli/cli/compose/types"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/container"
@@ -484,3 +485,37 @@ If a service is failing to even start, try smoke out the error with:
 `, appName, timeout, appName, appName, appName))
 	}
 }
+
+// Copypasta from https://github.com/docker/cli/blob/master/cli/command/stack/swarm/list.go
+// GetStacks lists the swarm stacks.
+func GetStacks(cl *dockerClient.Client) ([]*formatter.Stack, error) {
+	services, err := cl.ServiceList(
+		context.Background(),
+		types.ServiceListOptions{Filters: getAllStacksFilter()})
+	if err != nil {
+		return nil, err
+	}
+	m := make(map[string]*formatter.Stack)
+	for _, service := range services {
+		labels := service.Spec.Labels
+		name, ok := labels[convert.LabelNamespace]
+		if !ok {
+			return nil, errors.Errorf("cannot get label %s for service %s",
+				convert.LabelNamespace, service.ID)
+		}
+		ztack, ok := m[name]
+		if !ok {
+			m[name] = &formatter.Stack{
+				Name:     name,
+				Services: 1,
+			}
+		} else {
+			ztack.Services++
+		}
+	}
+	var stacks []*formatter.Stack
+	for _, stack := range m {
+		stacks = append(stacks, stack)
+	}
+	return stacks, nil
+}