I would like to add an attribute rule (calculation) to a feature service so that it automatically takes information from field 'A', runs a simple Arcade expression, and populate field 'B' with the result. Specifically, I would like this to calculation to happen when users edit this feature service in ArcGIS Online. When the user adds a new point to the feature service, ideally the attribute rule automatically takes the data input into field 'A', runs an Arcade expression, and populates field 'B' with the result of the Arcade expression. Is that possible for feature services or do I misunderstand attribute rules? I have attempted to access the Attribute Rules pane in ArcGIS pro to add the rule to the feature service, but I get a message indicating that the 'feature class corresponding to this view is read-only'. The feature service is 'editable' so what is meant by read-only? What am I missing? Thanks!.