feat(provider): add ApertoDNS Dynamic DNS provider

[1r0n3d3v3l0per]

Description

Add support for ApertoDNS Dynamic DNS provider.

ApertoDNS implements the ApertoDNS Protocol v1.2, a modern JSON-based API for Dynamic DNS updates with full backward compatibility with the legacy DynDNS2 protocol.

Features

• Modern API: Uses POST /.well-known/apertodns/v1/update with Bearer token authentication and JSON request/response
• Legacy Fallback: Automatic fallback to DynDNS2 GET /nic/update for maximum compatibility
• Configurable Base URL: Works with any ApertoDNS-compatible server via base_url parameter
• Full Error Handling: Proper handling of all error codes (invalid_token, hostname_not_found, rate_limited, etc.)

Configuration Example

{
  "settings": [
    {
      "provider": "apertodns",
      "domain": "apertodns.com",
      "owner": "home",
      "token": "your_api_token",
      "ip_version": "ipv4"
    }
  ]
}

Protocol Support

This provider implements both layers of the ApertoDNS Protocol:

1. Layer 2 (Modern): POST /.well-known/apertodns/v1/update - Primary method
2. Layer 1 (Legacy): GET /nic/update - Fallback for infrastructure errors

The provider intelligently uses the modern API first, falling back to legacy only for infrastructure errors (not for authentication or validation errors).

Testing

• go build ./... passes
• go vet ./... passes
• gofmt passes
• Integration tests pass (5/5)
• Manual testing with live API completed

Files Changed

• internal/provider/providers/apertodns/provider.go - New provider implementation
• internal/provider/providers/apertodns/provider_test.go - Integration tests
• internal/provider/constants/providers.go - Added ApertoDNS constant
• internal/provider/provider.go - Added import and case
• docs/apertodns.md - User documentation

Links

• Website: https://apertodns.com
• Protocol Specification: https://github.com/apertodns/apertodns-protocol
• API Documentation: https://apertodns.com/docs