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>

routers/repo/http.go

@@ -102,6 +102,7 @@ func HTTP(ctx *context.Context) {
 
 	owner, err := models.GetUserByName(username)
 	if err != nil {
+		log.Error("Attempted access of unknown user from %s", ctx.RemoteAddr())
 		ctx.NotFoundOrServerError("GetUserByName", models.IsErrUserNotExist, err)
 		return
 	}