BUG #17625: In PG15 PQsslAttribute returns different values than PG14 when SSL is not in use for the connection

The following bug has been logged on the website:

Bug reference:      17625
Logged by:          Heath Lord
Email address:      heath.lord@crunchydata.com
PostgreSQL version: Unsupported/Unknown
Operating system:   All
Description:

Hello folks,

I think I found a small bug on PG15.  My guess is it's a small documentation
issue, but I'll let the experts here decide.

According to the documentation
(https://www.postgresql.org/docs/15/libpq-status.html#LIBPQ-PQSSLATTRIBUTE),
PQsslAttribute should return NULL if the SSL implementation is not in use.
Here is the relevant line snipped from the documentation:

library
        Name of the SSL implementation in use. (Currently, only "OpenSSL" is
implemented)

According to the connection I am using, PQsslInUse is returning FALSE.
However, when I check the PQsslAttribute values, they are returning
"OpenSSL, NULL, NULL, NULL, NULL".  In PostgreSQL 14, the library returns
NULL when the connection is not using OpenSSL.

It looks like commit ebc8b7d4416d8e0dfb7c05132ef6182fd3daf885 changed this
behavior.

We found this issue since psycopg2 2.9.3 is failing its regression tests
when run against PG15 because it is assuming functionality according to the
documentation.  If the issue is just a documentation problem, we will gladly
raise a github issue for that extension suggesting that they make a fix
accordingly.  But, before doing so, we wanted to confirm if this is just a
documentation issue, or an accidental change in behavior.

Thanks!