documentation: Error handling for SSE subscription

[yyan-coursera]

What are you missing in the docs

Could you help provide instruction on how to do custom error handling if we are using GQL SSE subscription? My other non-subscription requests overrides DataFetcherExceptionHandler and the custom error handling works fine. However, it does not work with my subscription request, even for permission denied requests it shows as extensions={errorType=UNAVAILABLE, errorDetail=SERVICE_ERROR}. The official documentation: https://netflix.github.io/dgs/error-handling/ does not seem to cover error handling for subscription