There is a patch release for this in tcWebHooks but I am now reluctant to update TeamCity because of my reliance on it.
https://github.com/tcplugins/tcWebHooks/releases
This just makes me wish that there was native support in TeamCity for Slack messages (like a LOT of people use Slack) and/or some kind of native webhook support. The plugins available to help me do slack notifications have not (a) really been what I needed and/or (b) been very well maintained. tcWebHooks is the right approach I believe (open-ended webhook support), but has some issues with competing JAR files and some unfinished features that require modifying XML on the server itself.
Generalized webhook support would go a long way to making TC more integratable with the rest of the tools teams use.