Weight is not included in the issue hook

Summary

When updating an issue, the weight field isn't sent as part of the hook payload. We'd like to be able to use the weight when an issue is updated, without having to go back to the issue API every time.

Steps to reproduce

Update any field in any issue

What is the current bug behavior?

The weight field isn't sent

What is the expected correct behavior?

The weight field should be sent as part of the issue hook payload

Relevant logs and/or screenshots

{
  "object_kind": "issue",
  "event_type": "issue",
  "user": {
    "name": "Administrator",
    "username": "root",
    "avatar_url": "https://www.gravatar.com/avatar/e64c7d89f26bd1972efa854d13d7dd61?s=80&d=identicon"
  },
  "project": {
    "id": 1,
    "name": "things",
    "description": "",
    "web_url": "http://gitlab/stuff/things",
    "avatar_url": null,
    "git_ssh_url": "git@gitlab:stuff/things.git",
    "git_http_url": "http://gitlab/stuff/things.git",
    "namespace": "stuff",
    "visibility_level": 0,
    "path_with_namespace": "stuff/things",
    "default_branch": null,
    "ci_config_path": null,
    "homepage": "http://gitlab/stuff/things",
    "url": "git@gitlab:stuff/things.git",
    "ssh_url": "git@gitlab:stuff/things.git",
    "http_url": "http://gitlab/stuff/things.git"
  },
  "object_attributes": {
    "author_id": 1,
    "closed_at": null,
    "confidential": false,
    "created_at": "2018-06-01 14:23:15 UTC",
    "description": "Hello",
    "due_date": null,
    "id": 1,
    "iid": 1,
    "last_edited_at": null,
    "last_edited_by_id": null,
    "milestone_id": null,
    "moved_to_id": null,
    "project_id": 1,
    "relative_position": 1073742323,
    "state": "opened",
    "time_estimate": 0,
    "title": "Hello",
    "updated_at": "2018-06-01 15:40:28 UTC",
    "updated_by_id": 1,
    "url": "http://gitlab/stuff/things/issues/1",
    "total_time_spent": 0,
    "human_total_time_spent": null,
    "human_time_estimate": null,
    "assignee_ids": [

    ],
    "assignee_id": null,
    "action": "update"
  },
  "labels": [

  ],
  "changes": {
    "updated_at": {
      "previous": "2018-06-01 15:36:51 UTC",
      "current": "2018-06-01 15:40:28 UTC"
    }
  },
  "repository": {
    "name": "things",
    "url": "git@gitlab:stuff/things.git",
    "description": "",
    "homepage": "http://gitlab/stuff/things"
  }
}