# System events
TODO describe all system events
## Description

For system event we use Global increment field with negative value.

## List
| systemEventId | name | description |
| :-----------: | ---- | ----------- |
| 8 | Session was ended by session listener | |
| 63 | Message read |
| 5 | Remove entity from session |
| 4 | endCall |
| 3 | startCall |
| 2 | Add new entity in session |
| 1 | endSession |
| 0 | startSession |

### Start session system event

fromEntityId: Who triggered start session
examples:
1. Visitor send first message, then fromEntityId = visitor.entityId
2. Rake user app agent send invite, then fromEntityId = rakeUserApp.entityId
3. Visitor click on proactive message with enabled start session flag, then fromEntityId = visitor.entityId

## API

### Create system event

URL: core serivce
Method: POST
Headers:```{ Authorization }```
body:

{ 
    systemEventId: Number,
    from?: {
        entityId: Number,
        platformId: Number,
    }
}

> If from field is not setup, the event will be created from the bot name