Re: Allow logical replication to copy tables in binary format

1.
+      <para>
+       If true, initial data synchronization will be performed in binary format
+      </para></entry>
It's not just the initial table sync right? The table sync can happen
at any other point of time when ALTER SUBSCRIPTION ... REFRESH
PUBLICATION WITH (copy = true) is run.
How about - "If true, the subscriber requests publication for
pre-existing data in binary format"?

2.
Perhaps, this should cover the recommended cases for enabling this new
option - something like below (may not need to have exact wording, but
the recommended cases?):
"It is recommended to enable this option only when 1) the column data
types have appropriate binary send/receive functions, 2) not
replicating between different major versions or different platforms,
3) both publisher and subscriber tables have the exact same column
types (not when replicating from smallint to int or numeric to int8
and so on), 4) both publisher and subscriber supports COPY with binary
option, otherwise the table copy can fail."

> 3. I think the newly added tests must verify if the binary COPY is
> picked up when enabled. Perhaps, looking at the publisher's server log
> for 'COPY ... WITH BINARY format'? Maybe it's an overkill, otherwise,
> we have no way of testing that the option took effect.

Another way to test that BINARY is enabled could be to trigger one
of the failure cases.