Database: Supports events

[kettanaito]

Changes

• Adds a new public property "events" to the Database class.
• Supports three main events:
  • create: when a new entity is created;
  • update: when an existing entity is updated;
  • delete: when an existing entity is deleted.

Motivation

• Pre-requisite for Persistency layer #49, Server-Client synchronization #54

By adding events to the Database, it becomes possible to listen to when they occur:

db.events.on('create', (modelName, prevEntity, nextEntity) => {
  console.log('created a new entity', modelName)
})

Persistency and synchronization would use database events to know when to apply them to other database instances (i.e. in other clients, or to the server instance).