feat: add partial config support to talosctl cluster create

Allow passing a partial config to the machines using the `--input-dir` flag of `talosctl cluster create`.
With this change, it is not required to have talosconfig inside the input directory, neither for the configuration documents to contain a `v1alpha1` config document. They can solely contain maintenance config, e.g., `KmsgLogConfig`.

This is useful for testing scenarios such as partial machine configs being provided via cloud user data.

Signed-off-by: Utku Ozdemir <utku.ozdemir@siderolabs.com>

cmd/talosctl/cmd/mgmt/cluster/create.go

@@ -706,6 +706,17 @@ func create(ctx context.Context, flags *pflag.FlagSet) error {
 		return err
 	}
 
+	bundleTalosconfig := configBundle.TalosConfig()
+	if bundleTalosconfig == nil {
+		if clusterWait {
+			return errors.New("no talosconfig in the config bundle: cannot wait for cluster")
+		}
+
+		if applyConfigEnabled {
+			return errors.New("no talosconfig in the config bundle: cannot apply config")
+		}
+	}
+
 	if skipInjectingConfig {
 		types := []machine.Type{machine.TypeControlPlane, machine.TypeWorker}
 
@@ -827,8 +838,13 @@ func create(ctx context.Context, flags *pflag.FlagSet) error {
 		return err
 	}
 
+	// No talosconfig in the bundle - skip the operations below
+	if bundleTalosconfig == nil {
+		return nil
+	}
+
 	// Create and save the talosctl configuration file.
-	if err = saveConfig(configBundle.TalosConfig()); err != nil {
+	if err = saveConfig(bundleTalosconfig); err != nil {
 		return err
 	}