Add more docs for annotations/attributes

[provokateurin]

E.g. brute force protection information.

[provokateurin]

• \OCP\AppFramework\Http\Attribute\AnonRateLimit
• \OCP\AppFramework\Http\Attribute\BruteForceProtection
• \OCP\AppFramework\Http\Attribute\CORS
• \OCP\AppFramework\Http\Attribute\UserRateLimit

[provokateurin]

For rate limiting and bruteforce protection the 429 status code needs to be documented on the endpoints.