feat: add shell completion for ucind CLI (#344)

For feature parity with uc. Only _really_ usefull for ucind cluster rm,
but still useful, and not many lines of code.

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

cmd/ucind/cluster/remove.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/psviderski/uncloud/internal/ucind"
+	"github.com/psviderski/uncloud/internal/ucind/completion"
 	"github.com/spf13/cobra"
 )
 
@@ -26,6 +27,12 @@ func NewRemoveCommand() *cobra.Command {
 			fmt.Printf("Cluster '%s' removed.\n", name)
 			return nil
 		},
+		ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]cobra.Completion, cobra.ShellCompDirective) {
+			if len(args) > 0 {
+				return nil, cobra.ShellCompDirectiveNoFileComp
+			}
+			return completion.Clusters(cmd, args, toComplete)
+		},
 	}
 	return cmd
 }