User Experience: Allow users to add Description to Private Gateway and Static Routes

##### ISSUE TYPE

* Enhancement Request

##### COMPONENT NAME

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UI Enhancement
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##### CLOUDSTACK VERSION

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4.19
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##### CONFIGURATION

##### OS / ENVIRONMENT

N/A

##### SUMMARY

##### STEPS TO REPRODUCE

Currently, the Cloudstack UI doesnt support users to add descriptions/notes to their created Private Gateways and Static Routes

I propose adding descriptions To Private Gateways and Static Routes because as the number of gateways grows, i lose track of what each gateway was for, which makes it hard to maintain. And a Private Gateway can have many static routes, which are very hard to keep track too.

I see a large list, but i have no idea what each one is for. It becomes even worse if i have a colleague who adds another gateway and i have no i wont be able to identify (cause the list is so long) or understand what the item was created for.

I think this feature is one of those that are low hanging fruits that would greatly improve the users experience.

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##### EXPECTED RESULTS

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To be able to add descriptions to Private Gateways and Static Routes so its easier to maintain in the long term.
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##### ACTUAL RESULTS

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I add many private gateways and Static Routes without knowing its reference that its becoming very hard to maintain.
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issue #8837 に記載されている Private Gateways と Static Routes の UI フローから始め、影響を受ける CloudStack バージョンまたは main branch で現在の動作を確認してください。各リソースがどのように作成され、一覧表示されるかを追跡します。両方のリソースについてユーザーが説明を入力でき、作成された一覧を管理する際にその説明を確認できれば完了です。

索引モデルが issue の本文から書いたものです。