feat: ucind: implement cluster list command (#316)

* ucind: implement cluster list

I keep forgetting my ucind clusters, that add the missing list command:
```
% ./ucind cluster list
NAME    MACHINES
miek1   machine-1
```

Just the name would have been enough, but to actually make use of the
tui table a machines list is handy as well.
(There isn't much bubbletea in ucind, but I thought lets start now).

Signed-off-by: Miek Gieben <miek@miek.nl>

* Filter directly when listing

Filter on ucind managed while listing clusters

Signed-off-by: Miek Gieben <miek@miek.nl>

---------

Signed-off-by: Miek Gieben <miek@miek.nl>

cmd/ucind/cluster/ls.go

@@ -0,0 +1,40 @@
+package cluster
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/psviderski/uncloud/internal/cli/tui"
+	"github.com/psviderski/uncloud/internal/ucind"
+	"github.com/spf13/cobra"
+)
+
+func NewListCommand() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:     "ls",
+		Aliases: []string{"list"},
+		Short:   "List clusters.",
+		RunE: func(cmd *cobra.Command, args []string) error {
+			p := cmd.Context().Value("provisioner").(*ucind.Provisioner)
+			clusters, err := p.ListClusters(cmd.Context())
+			if err != nil {
+				return fmt.Errorf("list clusters: %w", err)
+			}
+			t := tui.NewTable()
+			t.Headers("NAME", "MACHINES")
+			for _, cluster := range clusters {
+				machines := []string{}
+				for _, m := range cluster.Machines {
+					machines = append(machines, m.Name)
+				}
+				t.Row(
+					cluster.Name,
+					strings.Join(machines, tui.Faint.Render(", ")),
+				)
+			}
+			fmt.Println(t)
+			return nil
+		},
+	}
+	return cmd
+}

cmd/ucind/cluster/root.go

@@ -13,7 +13,7 @@ func NewRootCommand() *cobra.Command {
 	}
 	cmd.AddCommand(
 		NewCreateCommand(),
-		// NewListCommand(),
+		NewListCommand(),
 		NewRemoveCommand(),
 	)
 	return cmd