Re: Add ssl_(supported|shared)_groups to sslinfo

+ /*
+ * SSL_group_to_name can return NULL in case of an error, e.g. when no
+ * such name was registered for some reason.
+ */
+ group_name = SSL_group_to_name(ssl, nid);
+ if (group_name == NULL)
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("unknown OpenSSL group at position %d",
+ call_cntr)));

I'm not sure if erroring out is the proper approach here. Won't this
mean that with a newer openssl version on the client side, the
function will potentially simply error out instead of returning proper
results?
For example, we could report

values[1] = StringGetTextDatum(psprintf("unknown (0x%04x)", nid & 0xffff));

in this case?

@@ -2901,6 +2904,8 @@ decl_checks = [
['strlcpy', 'string.h'],
['strsep', 'string.h'],
['timingsafe_bcmp', 'string.h'],
+ ['SSL_get1_groups', 'openssl/ssl.h'],
+ ['SSL_get_negotiated_group', 'openssl/ssl.h'],

This list isn't OpenSSL-aware, these won't get proper dependencies,
these should go inside the ssl.found() block

+#else
+ /* SSL groups API is not present, skip */
+ MemoryContextSwitchTo(oldcontext);
+ SRF_RETURN_DONE(funcctx);
+#endif

Shouldn't this branch have some documentation / diagnostics so it's
not a completely silent/undocumented skip?

And in the commit message:

select * from ssl_group_info();
type | name
------------+--------------------

That seems to be at typo/earlier leftover as it should be group_type now?