feat(UX): Show a warning when bruteforce protection is throttling

[nickvergessen]

☑️ Resolves

For testing add:

$response->addHeader('X-Nextcloud-Bruteforce-Throttled', '25000ms');

Before
https://github.com/nextcloud/server/blob/25309bcb45232bf30fe719bac1776f0136f7cd7a/lib/private/AppFramework/Middleware/Security/BruteForceMiddleware.php#L136

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not possible
• 📘 API documentation in docs/ has been updated or is not required
• 🔖 Capability is added or not needed

[Antreesy]

Looks ok
Can we include request ID or user IP for backtracking?

[nickvergessen]

Well that will be any "join" of a conversation. But yeah might make sense to add some info the sysadmin can find locally