Insertion into tables with generated columns causes shape termination

[AntonOfTheWoods]

To reproduce, add the following main...AntonOfTheWoods:electric:generated_bug and do a normal run of the todo-app example. Any insertion (e.g, via the demo web interface) causes the following message in the log:

01:12:57.837 pid=<0.3097.0> shape_handle=91872063-1737681148357 [info] Schema for the table "public"."todos" changed - terminating shape 91872063-1737681148357

This, in turn, causes a must-revalidate on all clients and the obligatory re-syncing of the entire shape

[balegas]

Electric does not handle generated columns and seems unlikely that it will since they are skipped in logical replication https://www.postgresql.org/docs/current/ddl-generated-columns.html. We need to look into the messages in the replication stream to see if we can handle the special case.