Ensure single IPv6 record per subdomain in Cloudflare provider

[Claude]

During network restarts with rapid IPv6 address changes, multiple AAAA records accumulate for the same subdomain in Cloudflare, leaving both valid and stale IP addresses that cause connectivity issues.

Changes

• Added deleteRecord method: Implements DNS record deletion via Cloudflare API DELETE endpoint

• Refactored UpdateIP logic:

  • Changed from strings.Contains() to exact domain name matching (rec.Name == fullDomainName)
  • Collects all matching records for a subdomain before processing
  • Updates the first record with correct IP or keeps it if already correct
  • Deletes all duplicate records in a cleanup pass

Behavior

Before: Multiple AAAA records could exist for the same subdomain

service.example.com -> 2001:db8::a34d:163a:dc1c
service.example.com -> 2001:db8::c8ab:790:5b7  (stale)

After: Only one record remains per subdomain

service.example.com -> 2001:db8::a34d:163a:dc1c

Duplicate deletion failures are logged but don't prevent successful IP updates.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Cloudflare 确保每个子域名仅有一个 IPv6 地址</issue_title>
<issue_description>有时主机网络在重启过程中出现 IP 反复横跳的问题：

Mar 20 21:46:18 godns[991]: time="2025-03-20T21:46:18+08:00" level=info msg="Checking IP for domain ***1.example.com"
Mar 20 21:46:19 godns[991]: time="2025-03-20T21:46:19+08:00" level=info msg="Querying records with type: AAAA"
Mar 20 21:46:29 godns[991]: time="2025-03-20T21:46:29+08:00" level=error msg="Request error:Get \"https://api.cloudflare.com/client/v4/zones/****/dns_records?type=AAAA&page=1&per_page=500\": context deadline exceeded (Client.Timeout exceeded while awaiting headers)"
Mar 20 21:46:30 godns[991]: time="2025-03-20T21:46:30+08:00" level=info msg="Record [service] created with IP address: ****:a34d:163a:dc1c"
Mar 20 21:46:31 godns[991]: time="2025-03-20T21:46:31+08:00" level=info msg="Checking IP for domain ***2.example.com"
Mar 20 21:46:32 godns[991]: time="2025-03-20T21:46:32+08:00" level=info msg="Querying records with type: AAAA"
Mar 20 21:46:32 godns[991]: time="2025-03-20T21:46:32+08:00" level=info msg="IP mismatch: Current(****:a34d:163a:dc1c) vs Cloudflare(****:c8ab:790:5b7)"
Mar 20 21:46:33 godns[991]: time="2025-03-20T21:46:33+08:00" level=info msg="Record updated: ***2.example.com - ****:a34d:163a:dc1c"
Mar 20 21:56:54 godns[991]: time="2025-03-20T21:56:54+08:00" level=info msg="Checking IP for domain ***1.example.com"
Mar 20 21:56:54 godns[991]: time="2025-03-20T21:56:54+08:00" level=info msg="Querying records with type: AAAA"
Mar 20 21:56:55 godns[991]: time="2025-03-20T21:56:55+08:00" level=info msg="IP mismatch: Current(****:c8ab:790:5b7) vs Cloudflare(****:a34d:163a:dc1c)"
Mar 20 21:56:56 godns[991]: time="2025-03-20T21:56:56+08:00" level=info msg="Record updated: ***2.example.com - ****:c8ab:790:5b7"
Mar 20 21:56:56 godns[991]: time="2025-03-20T21:56:56+08:00" level=info msg="IP mismatch: Current(****:c8ab:790:5b7) vs Cloudflare(****:a34d:163a:dc1c)"
Mar 20 21:56:57 godns[991]: time="2025-03-20T21:56:57+08:00" level=info msg="Response failed: "
Mar 20 21:56:57 godns[991]: time="2025-03-20T21:56:57+08:00" level=info msg="Record OK: ***1.example.com - ****:c8ab:790:5b7"
Mar 20 21:56:57 godns[991]: time="2025-03-20T21:56:57+08:00" level=info msg="Checking IP for domain ***2.example.com"
Mar 20 21:56:58 godns[991]: time="2025-03-20T21:56:58+08:00" level=info msg="Querying records with type: AAAA"
Mar 20 21:56:59 godns[991]: time="2025-03-20T21:56:59+08:00" level=info msg="Record OK: ***2.example.com - ****:c8ab:790:5b7"

最终，两个 IP 都在 Cloudflare 中留下了，但实际只有一个能用，访问的时候就会访问到已失效的地址。
如何在每次更新时确保子域名只有一个 IP？</issue_description>

Comments on the Issue (you are @claude[agent] in this section)

@TimothyYe 运营商给你分配了不止一个IPv6地址吗？

• Fixes Cloudflare 确保每个子域名仅有一个 IPv6 地址 #268