Add crud endpoints for notifications (#801)

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/801
Co-authored-by: konrad <konrad@kola-entertainments.de>
Co-committed-by: konrad <konrad@kola-entertainments.de>

pkg/events/listeners.go

@@ -20,7 +20,7 @@ import "github.com/ThreeDotsLabs/watermill/message"
 
 // Listener represents something that listens to events
 type Listener interface {
-	Handle(payload message.Payload) error
+	Handle(msg *message.Message) error
 	Name() string
 }