fix: Adjust PostRenderer plugin output to value

Signed-off-by: George Jenkins <gvjenkins@gmail.com>

internal/plugin/runtime_subprocess.go

@@ -270,7 +270,7 @@ func (r *SubprocessPluginRuntime) runPostrenderer(input *Input) (*Output, error)
 	}
 
 	return &Output{
-		Message: &schema.OutputMessagePostRendererV1{
+		Message: schema.OutputMessagePostRendererV1{
 			Manifests: postRendered,
 		},
 	}, nil

pkg/postrenderer/postrenderer.go

@@ -73,7 +73,7 @@ func (r *postRendererPlugin) Run(renderedManifests *bytes.Buffer) (*bytes.Buffer
 		return nil, fmt.Errorf("failed to invoke post-renderer plugin %q: %w", r.plugin.Metadata().Name, err)
 	}
 
-	outputMessage := output.Message.(*schema.OutputMessagePostRendererV1)
+	outputMessage := output.Message.(schema.OutputMessagePostRendererV1)
 
 	// If the binary returned almost nothing, it's likely that it didn't
 	// successfully render anything