test_ddl_deparse is an example of how to use the pg_ddl_command datatype.
It is not intended to do anything useful on its own; rather, it is a
demonstration of how to use the datatype, and to provide some unit tests for
it.

The functions in this extension are intended to be able to process some
part of the struct and produce some readable output, preferably handling
all possible cases so that SQL test code can be written.