Add notification hook and run summary

internal/notify/notify.go

@@ -0,0 +1,25 @@
+package notify
+
+import "context"
+
+type Event struct {
+	PipelineID    string
+	DestinationID string
+	BundleID      string
+	BundlePath    string
+	Action        string
+	Outputs       []Output
+}
+
+type Output struct {
+	Path       string
+	Kind       string
+	SourcePath string
+	Transform  string
+	SHA256     string
+	Size       int64
+}
+
+type Notifier interface {
+	Notify(ctx context.Context, event Event) error
+}