Bug model derived from Webhook payload

[leplatrem]

The current bug model has a comment and an attachment field.

jira-bugzilla-integration/jbi/bugzilla/models.py

Lines 126 to 127 in 3f8bf31

	comment: Optional[WebhookComment] = None
	attachment: Optional[WebhookAttachment] = None

Because that is what the Webhook payload sends us when target == 'comment' or target == 'attachment'.

Example with this event:

event: {
        "target": "attachment",
        "changes": null,
        "time": "datetime.datetime(2025, 10, 16, 11, 52, 57, tzinfo=TzInfo(0))",
        "user": {
          "login": "mathieu@mozilla.com",
          "real_name": "Mathieu Leplatre [:leplatrem]",
          "id": 526079
        },
        "routing_key": "attachment.create",
        "action": "create"
},
bug: {
        "priority": "",
        "resolution": "",
        "type": "enhancement",
        "keywords": [],
        "is_private": false,
        "creator": "mathieu@mozilla.com",
        "assigned_to": "nobody@mozilla.org",
        "see_also": [
          "https://mozilla-hub.atlassian.net/browse/RMST-161"
        ],
        "whiteboard": "[remote-settings]",
        "comment": null,
        "groups": null,
        "status": "NEW",
        "id": 1984079,
        "cf_fx_points": "",
        "attachment": {
          "content_type": "text/x-phabricator-request",
          "flags": [],
          "is_private": false,
          "is_obsolete": false,
          "description": "Bug 1984079 - Iterate through list of signatures r?say-yawn",
          "file_name": "phabricator-D268863-url.txt",
          "id": 9520447,
          "is_patch": false,
          "creation_time": "datetime.datetime(2025, 10, 16, 11, 52, 57, tzinfo=TzInfo(0))"
        },
        "summary": "Add support for multiple signatures in the collection metadata",
        "product": "Firefox",
        "severity": "--",
        "component": "Remote Settings Client",
        "flags": []
      }

But conceptually, a bug has several attachments and comments.

We should probably split that model and introduce a WebhookRequestBug model that differs from just Bug