upstream: document Match invalid-user

OpenBSD-Commit-ID: 2c84a9b517283e9711e2812c1f268081dcb02081

Author: djmdjm

sshd.8

@@ -33,8 +33,8 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: sshd.8,v 1.326 2024/06/17 08:30:29 djm Exp $
-.Dd $Mdocdate: June 17 2024 $
+.\" $OpenBSD: sshd.8,v 1.327 2024/09/15 01:19:56 djm Exp $
+.Dd $Mdocdate: September 15 2024 $
 .Dt SSHD 8
 .Os
 .Sh NAME
@@ -115,6 +115,10 @@ and
 .Dq rdomain
 and correspond to source address, user, resolved source host name,
 local address, local port number and routing domain respectively.
+Additionally the
+.Dq invalid-user
+flag (which does not take a value argument) may be specified to simulate
+a connection from an unrecognised username.
 .It Fl c Ar host_certificate_file
 Specifies a path to a certificate file to identify
 .Nm