Pass context to event publishing.

To allow tracing propagation via events, we need to pass the context
to the `Publish` function of reva events. This adds the context
everywhere where events are published. If there was no context to pass,
we started a new one with `context.Background()`.

services/graph/pkg/service/v0/educationclasses.go

@@ -185,7 +185,7 @@ func (g Graph) PatchEducationClass(w http.ResponseWriter, r *http.Request) {
 		if currentUser, ok := revactx.ContextGetUser(r.Context()); ok {
 			e.Executant = currentUser.GetId()
 		}
-		g.publishEvent(e)
+		g.publishEvent(r.Context(), e)
 
 	}