NETCUP: fixup provider to make it pass the latest integration test suite

[kordianbruck]

This pull request introduces several improvements and fixes to the Netcup provider, focusing on better API usage, improved error handling, and stricter auditing for record compatibility. The most significant change is batching record modifications into a single API call, which streamlines updates and reduces rate limit issues. Additionally, new auditing checks are added, and the provider now verifies domain authority before returning nameservers.

Netcup Provider Improvements

• Batch record updates: Replaces individual create, modify, and delete API calls with a single updateRecords method that batches all record changes into one API request, improving efficiency and respecting Netcup's rate limits. [1] [2]
• API rate limiting: Introduces a 334ms delay after each API call to comply with Netcup's documented rate limit of 180 requests per minute.
• Improved error messages: Enhances error reporting by including the action, status code, and full API response in error messages.

Record Auditing and Validation

• New auditing rules: Adds checks to reject TXT records with backslashes, single quotes, or double quotes, and CAA records with semicolons, based on Netcup API behavior. [1] [2]
• Test and integration updates: Updates integration tests and disables TTL-related tests for Netcup, reflecting its lack of support for custom TTLs and per-record TTLs. [1] [2]

Provider Behavior

• Nameserver authority check: The provider now verifies domain authority with an API call before returning nameservers, ensuring accurate error handling for unmanaged domains.

[TomOnTime]

Perfect! Thanks!