We want to give users ability to listen on events only when certain columns change for a record. Currently, we send events when the record changes even if certain columns did not change.

We have two options:

1. Simple: Listen on specified columns but send entire record as payload.
2. Full : Listen on specified columns and send (some other) specified columns as payload.

1 is easy to understand. 2 is somewhat confusing as there are now two types of column expressions.