Document SSL_set_psk_find_session_callback() and SSL_CTX equivalent

Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3670)

doc/man3/SSL_CTX_set_psk_client_callback.pod

@@ -106,7 +106,7 @@ should not be freed by the application.
 
 It is also possible for the callback to succeed but not supply a PSK. In this
 case no PSK will be sent to the server but the handshake will continue. To do
-this the callback should return successfully and ensure that the B<*sess> is
+this the callback should return successfully and ensure that B<*sess> is
 NULL. The contents of B<*id> and B<*idlen> will be ignored.
 
 =head1 NOTES

doc/man3/SSL_CTX_use_psk_identity_hint.pod

@@ -77,6 +77,11 @@ case no PSK will be used but the handshake will continue. To do this the
 callback should return successfully and ensure that B<*sess> is
 NULL.
 
+=head1 NOTES
+
+A connection established via a TLSv1.3 PSK will appear as if session resumption
+has occurred so that L<SSL_session_reused(3)> will return true.
+
 =head1 RETURN VALUES
 
 SSL_CTX_use_psk_identity_hint() and SSL_use_psk_identity_hint() return

util/private.num

@@ -23,6 +23,8 @@ OPENSSL_Applink                         external
 SSL_CTX_keylog_cb_func                  datatype
 SSL_early_cb_fn                         datatype
 SSL_psk_client_cb_func                  datatype
+SSL_psk_find_session_cb_func            datatype
+SSL_psk_server_cb_func                  datatype
 SSL_psk_use_session_cb_func             datatype
 SSL_verify_cb                           datatype
 UI                                      datatype