[New Feature] Event generation - Details of the event in payload

[sidd-kulk]

In Medusa 2.0, we can create subscribers to consume events generated by the framework. These events only have the id of the entity (e.g. product id for product events). There are no related data and attributes included in it. This makes it difficult to snapshot the state of the system at that particular time. Usually, any such events are used as an audit trail, but without a data snapshot, it has limited usability.

Ideal event structure:

`

{
    "eventId" : "xxx",
    "eventType" : "product.updated",
    "timestamp" : "xxx",
    "payload": {
          "id" : "product id",
          "name" : "product name",
           ...
    }
}