Support OpenTelemetry event attributes

[alexbikfalvi]

User problem

When sending OpenTelemetry events, the Trace View span details only shows the event's name, no additional data.

The respective Grafana panel showing span details should show not only the event's name but also additional data. This feature is fairly important for OpenTelemetry users, who attach important attributes to those events that help them track the processing of entities. Without those attributes, they cannot identify which entity is being handled or we cannot follow the "path" of an entity throughout our system.

Without being able to see event attributes, users still benefit a lot from the Grafana tracing integration but they have to implement workarounds to have all the data we need to interpret the traces efficiently in high-load or erroneous scenarios.