Mattermost Mattermost is an open-source, self-hosted team collaboration platform similar to Slack. It's used by organizations, especially those with strict security or compliance requirements, for internal communication and project management. Official docs: https://developers.mattermost.com/ Mattermost Overview - Channel - Post - User Use action names and parameters as needed. Working with Mattermost This skill uses the Membrane CLI to interact with Mattermost. Membrane handles authentication and credentials refresh automatically — so you can focus on the integration logic rather than auth p…