Improve Jira integration's "commented" event notification.

Currently, our Jira integration supports comment-related events. However, when a comment includes a mention of other users, the webhook payload does not include the display name of the mentioned user. As a result, it is formatted using the account ID.

The comment in Jira:

The notification in Zulip:

{
  "timestamp": 1722411493985,
  "webhookEvent": "comment_created",
  "comment": {
    "self": "https://peteririri.atlassian.net/rest/api/2/issue/10002/comment/10003",
    "id": "10003",
    "author": {
      "self": "https://peteririri.atlassian.net/rest/api/2/user?accountId=619a4432ebce470067f20384",
      "accountId": "619a4432ebce470067f20384",
      "avatarUrls": {
        "48x48": "https://secure.gravatar.com/avatar/338c91613dac07cd4bd32682a494fe66?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FP-5.png",
        "24x24": "https://secure.gravatar.com/avatar/338c91613dac07cd4bd32682a494fe66?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FP-5.png",
        "16x16": "https://secure.gravatar.com/avatar/338c91613dac07cd4bd32682a494fe66?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FP-5.png",
        "32x32": "https://secure.gravatar.com/avatar/338c91613dac07cd4bd32682a494fe66?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FP-5.png"
      },
      "displayName": "Peter",
      "active": true,
      "timeZone": "Asia/Jakarta",
      "accountType": "atlassian"
    },
    "body": "[~accountid:619a4432ebce470067f20384] [~accountid:63a22fb348b367d78a14c15b] ",
    "updateAuthor": {
      "self": "https://peteririri.atlassian.net/rest/api/2/user?accountId=619a4432ebce470067f20384",
      "accountId": "619a4432ebce470067f20384",
      "avatarUrls": {
        "48x48": "https://secure.gravatar.com/avatar/338c91613dac07cd4bd32682a494fe66?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FP-5.png",
        "24x24": "https://secure.gravatar.com/avatar/338c91613dac07cd4bd32682a494fe66?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FP-5.png",
        "16x16": "https://secure.gravatar.com/avatar/338c91613dac07cd4bd32682a494fe66?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FP-5.png",
        "32x32": "https://secure.gravatar.com/avatar/338c91613dac07cd4bd32682a494fe66?d=https%3A%2F%2Favatar-management--avatars.us-west-2.prod.public.atl-paas.net%2Finitials%2FP-5.png"
      },
      "displayName": "Peter",
      "active": true,
      "timeZone": "Asia/Jakarta",
      "accountType": "atlassian"
    },
    "created": "2024-07-31T14:38:13.985+0700",
    "updated": "2024-07-31T14:38:13.985+0700",
    "jsdPublic": true
  },
  "issue": {
    "id": "10002",
    "self": "https://peteririri.atlassian.net/rest/api/2/10002",
    "key": "SB-1",
    "fields": {
      "summary": "asdasd",
      "issuetype": {
        "self": "https://peteririri.atlassian.net/rest/api/2/issuetype/10002",
        "id": "10002",
        "description": "Functionality or a feature expressed as a user goal.",
        "iconUrl": "https://peteririri.atlassian.net/rest/api/2/universal_avatar/view/type/issuetype/avatar/10315?size=medium",
        "name": "Story",
        "subtask": false,
        "avatarId": 10315,
        "hierarchyLevel": 0
      },
      "project": {
        "self": "https://peteririri.atlassian.net/rest/api/2/project/10001",
        "id": "10001",
        "key": "SB",
        "name": "scrum board",
        "projectTypeKey": "software",
        "simplified": false,
        "avatarUrls": {
          "48x48": "https://peteririri.atlassian.net/rest/api/2/universal_avatar/view/type/project/avatar/10401",
          "24x24": "https://peteririri.atlassian.net/rest/api/2/universal_avatar/view/type/project/avatar/10401?size=small",
          "16x16": "https://peteririri.atlassian.net/rest/api/2/universal_avatar/view/type/project/avatar/10401?size=xsmall",
          "32x32": "https://peteririri.atlassian.net/rest/api/2/universal_avatar/view/type/project/avatar/10401?size=medium"
        }
      },
      "assignee": null,
      "priority": {
        "self": "https://peteririri.atlassian.net/rest/api/2/priority/3",
        "iconUrl": "https://peteririri.atlassian.net/images/icons/priorities/medium.svg",
        "name": "Medium",
        "id": "3"
      },
      "status": {
        "self": "https://peteririri.atlassian.net/rest/api/2/status/10007",
        "description": "",
        "iconUrl": "https://peteririri.atlassian.net/",
        "name": "To Do",
        "id": "10007",
        "statusCategory": {
          "self": "https://peteririri.atlassian.net/rest/api/2/statuscategory/2",
          "id": 2,
          "key": "new",
          "colorName": "blue-gray",
          "name": "To Do"
        }
      }
    }
  },
  "eventType": "primaryAction"
}

To improve notification for this event, we want to do a callback to this Jira API to fetch the display name of the mentioned user.

---

Blocked on adding config_options for integration bots to be able to store to BotConfigData such as API keys. See https://github.com/zulip/zulip/pull/38279#discussion_r3019500289.

Other resource: Generate API token for Jira user

CZO thread