Campfire
Campfire is web-based chat application. It supports many of the features you'd expect, including:
Multiple rooms, with access controls
Direct messages
File attachments with previews
Search
Notifications (via Web Push)
@mentions
API, with support for bot integrations
Campfire is single-tenant: any rooms designated "public" will be accessible by all users in the system. To support entirely distinct groups of customers, you would deploy multiple instances of the application.
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