DNS resolution across VPCs connected via S2S VPN

##### ISSUE TYPE

* Feature Idea

##### COMPONENT NAME

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VR
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##### CLOUDSTACK VERSION

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4.20
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##### CONFIGURATION

##### OS / ENVIRONMENT

##### SUMMARY

Current VR only resolve its own Guest Network DNS zone record and external records. When two or more peered VPC network, user has to manage the host resolution either by host file or create another forwarder point to VR in upstream DNS. I would say it would be more useful if we populate all DNS record across each peered zone VR with proper domain suffix. So the user do not need to discover new IP changes from peered zone.

##### STEPS TO REPRODUCE

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##### EXPECTED RESULTS

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##### ACTUAL RESULTS

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先檢查 CloudStack VR 元件，以及在 4.20 版本中如何表示已建立對等連線的 VPC DNS 區域。在確定相關實作和測試之前，釐清預期的網域後綴、記錄傳播行為和面向使用者的使用方式；完成的標準是，無需管理 hosts 檔案或上游轉送器，DNS 解析即可在已建立對等連線的 VPC 之間正常運作。

由索引模型根據 Issue 內容生成。