Allow attaching multiple components to an incident with the API

[itsnewtjam]

This addresses issue #156

Supports attaching multiple components when creating an incident via API:

{
  "name": "<string>",
  "status": 0,
  "message": "<string>",
  "template": "<string>",
  "visible": false,
  "stickied": false,
  "notifications": false,
  "occurred_at": "<string>",
  "template_vars": [],
  "components": [
    {
      "component_id": 123,
      "component_status": 1
    },
    // etc...
  ]
}

Also:

• pulls the first component for the component template variable, just in case :)
• removes associated rows in the incident_components table when an incident is deleted

[jbrooksuk]

This is great work, thanks @itsnewtjam. Could you please add a test case for this and then we can get it merged.

[itsnewtjam]

@jbrooksuk Test added! Not sure why the CreateMetricPoint test failed in the checks though, seems unrelated and it's passing fine locally