event: missing notification on pipeline cancellation

[mutezero]

JSON won't tell who or why it was cancelled, assume it was made manually by any user with the access.

Here's an example:

{
  "object_kind": "pipeline",
  "object_attributes": {
    "id": 413,
    "ref": "master",
    "tag": false,
    "sha": "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
    "before_sha": "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa0",
    "status": "canceled",
    "detailed_status": "canceled",
    "stages": [
      "cleanup_pre",
      "checkout",
      "deploy"
    ],
    "created_at": "2018-12-08 06:35:44 UTC",
    "finished_at": "2018-12-08 06:38:50 UTC",
    "duration": 179,
    "variables": []
  },
  "user": {
    "name": "DisplayName",
    "username": "username",
    "avatar_url": "https://example.com/uploads/-/system/user/avatar/2/avatar.png"
  },
  "project": {
    "id": 1,
    "name": "Repo1",
    "description": "",
    "web_url": "https://example.com/team-a/repo1",
    "avatar_url": "https://example.com/uploads/-/system/project/avatar/1/repo1_logo.png",
    "git_ssh_url": "[email protected]:team-a/repo1.git",
    "git_http_url": "https://example.com/team-a/repo1.git",
    "namespace": "Team A",
    "visibility_level": 20,
    "path_with_namespace": "team-a/repo1",
    "default_branch": "master",
    "ci_config_path": ""
  },
  "commit": {
    "id": "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
    "message": "Merge branch 'develop' into 'master'\n\nSee merge request team-a/repo1!142",
    "timestamp": "2018-12-08T06:35:42Z",
    "url": "http://example.com/team-a/repo1/commit/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
    "author": {
      "name": "DisplayName",
      "email": "[email protected]"
    }
  },
  "builds": [
    {
      "id": 2608,
      "stage": "deploy",
      "name": "deploy:server",
      "status": "canceled",
      "created_at": "2018-12-08 06:35:45 UTC",
      "started_at": null,
      "finished_at": "2018-12-08 06:38:50 UTC",
      "when": "on_success",
      "manual": false,
      "user": {
        "name": "DisplayName",
        "username": "username",
        "avatar_url": "http://example.com/uploads/-/system/user/avatar/2/avatar.png"
      },
      "runner": null,
      "artifacts_file": {
        "filename": null,
        "size": 0
      }
    }
  ]
}