Log IP on SSH authentication failure for Built-in SSH server (#13150)

* Log IP on SSH authentication failure

fixes https://github.com/go-gitea/gitea/issues/13094

* include string 'Failed authentication attempt' in error

* update fail2ban docs

also match failed authentication over command line

* better logging of authentication errors with IP addresses

* format ...

Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: 6543 <6543@obermui.de>

modules/ssh/ssh.go

@@ -186,7 +186,7 @@ func publicKeyHandler(ctx ssh.Context, key ssh.PublicKey) bool {
 
 	pkey, err := models.SearchPublicKeyByContent(strings.TrimSpace(string(gossh.MarshalAuthorizedKey(key))))
 	if err != nil {
-		log.Error("SearchPublicKeyByContent: %v", err)
+		log.Error("SearchPublicKeyByContent: %v Failed authentication attempt from %s", err, ctx.RemoteAddr())
 		return false
 	}