fix: Expand the logging around AggregateError

[AnuragEkkati]

📝 Summary of changes done and why they are done

When axios requests fail with an AggregateError, the error logs just show "AggregateError" which provides no useful debugging information.

📋 Related issues

• Relates to AggregateError does not have good support for logging which n errors occurred #6482
• Resolves AggregateError does not have good support for logging which n errors occurred #6482

📄 Checklist

Please follow this checklist to avoid unnecessary back and forth (click to expand)

• ⚠️ If there are Breaking change (a fix or feature that alters existing functionality in a way that could cause issues) I have called them out
• 🧠 I have disclosed any use of LLMs/AI in this contribution and reviewed all generated content.
  I understand that I am responsible for and able to explain every line of code I submit.
• 🔍 My code adheres to the style guidelines of this project.
• ⚠️ My changes generate no new warnings.
• 🛠️ I have reviewed and tested my code.
• 📝 I have commented my code, especially in hard-to-understand areas (e.g., using JSDoc for methods).
• 🤖 I added or updated automated tests where appropriate.
• 📄 Documentation updates are included (if applicable).
• 🔒 I have considered potential security impacts and mitigated risks.
• 🧰 Dependency updates are listed and explained.

AI Usage

Cursor AI : GPT-5. Used to generate multiple testcases which can validate if existing functionality is not broken and new desired logging works as expected.

📷 Screenshots or Visual Changes

• Log Modifications: Logging around AggregateError changed

Before :

Error: Error: AggregateError
    at Slack.throwGeneralAxiosError (/Users/anurag/workspace/github/uptimekuma/uptime-kuma-test/server/notification-providers/notification-provider.js:122:15)
    at Slack.send (/Users/anurag/workspace/github/uptimekuma/uptime-kuma-test/server/notification-providers/slack.js:175:18)
    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)
    at async Socket.<anonymous> (/Users/anurag/workspace/github/uptimekuma/uptime-kuma-test/server/server.js:1568:27)

Error: Error: AxiosError: Request failed with status code 500 boom
    at Slack.throwGeneralAxiosError (/Users/anurag/workspace/github/uptime-kuma/server/notification-providers/notification-provider.js:122:15)
    at Slack.send (/Users/anurag/workspace/github/uptime-kuma/server/notification-providers/slack.js:175:18)
    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)
    at async Socket.<anonymous> (/Users/anurag/workspace/github/uptime-kuma/server/server.js:1567:27)

After :

Error: Request failed (code=ECONNREFUSED) - caused by: connect ECONNREFUSED ::1:9999 (code=ECONNREFUSED); connect ECONNREFUSED 127.0.0.1:9999 (code=ECONNREFUSED)
    at Slack.throwGeneralAxiosError (/Users/anurag/workspace/github/uptimekuma/uptime-kuma-agg-error/server/notification-providers/notification-provider.js:158:15)
    at Slack.send (/Users/anurag/workspace/github/uptimekuma/uptime-kuma-agg-error/server/notification-providers/slack.js:170:18)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async Socket.<anonymous> (/Users/anurag/workspace/github/uptimekuma/uptime-kuma-agg-error/server/server.js:1564:27)

Error: Request failed with status code 500 (code=ERR_BAD_RESPONSE) (HTTP 500 Internal Server Error) boom
    at Slack.throwGeneralAxiosError (/Users/anurag/workspace/github/uptimekuma/uptime-kuma-agg-error/server/notification-providers/notification-provider.js:158:15)
    at Slack.send (/Users/anurag/workspace/github/uptimekuma/uptime-kuma-agg-error/server/notification-providers/slack.js:170:18)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async Socket.<anonymous> (/Users/anurag/workspace/github/uptimekuma/uptime-kuma-agg-error/server/server.js:1564:27)

UI	Before	After
UI Message

[CommanderStorm]

Looks good to me.

I would like to see the testcase be made a bit more understandable, if possible, that is currently not entirely the case