How to configure Rasa on Openshift for Mattermost?

Rasa 1.10.3, Rasa X 0.30 on Openshift.

I can’t figure out how to configure Rasa on Openshift as to get Mattermost as communication channel.

Off-course I read the docs and this, although for 0.32 instead of 0.30.

But this still doesn’t make clear to me, where and how to connect Mattermost and Rasa .