Notifications system

We define a notifications format in 7 properties:

• service (e.g. GitHub)
• project (e.g. Nasqueron)
• group (e.g. Tasacora)
• rawContent (e.g. the payload from GitHub API)
• type (e.g. push or task)
• text (a short textual description of the notification)
• link (an URL to the most relevant link to get more information)

We implement this notification system for GitHub payloads.