Implement flags for targeting an execution environment during deployment

deploy と write-manifest のコマンドエントリポイントから始め、既存の --image フラグと環境フィールドがどのように処理されているかを確認します。default_image_name と default_environment_guid の Connect App 更新パスを追跡します。両方のコマンドとワークフローをカバーし、新しいフラグが要求されたマニフェスト値を書き込むか、指定どおりに App のデフォルト値を永続化すれば完了です。

Connect 2025.04 allows setting environment.identifier in the bundle's manifest.json. This new field allows the content to target a specific execution environment when running on Connect. The existing environment.image field remains unchanged however the semantics are slightly different. An image selection is now treated the same as any other piece of matching criteria. Connect will choose any execution environment that uses the specified container image.

We should add an --environment-id flag to both deploy <app> and write-manifest <app> - the value is the guid of the target execution environment in Connect and it should be written to environment.identifier in the manifest.json.

We should also add arguments the following arguments to deploy <app>: --default-image and --default-environment-id. These arguments accepts an image name and an execution environment guid respectively, however instead of writing these to the manfiest.json, we should update the App record in Connect to set the app.default_image_name and app.default_environment_guid fields. This new workflow allows users to call deploy <app> --default-image='my/custom/image:latest' or deploy <app> --default-environment-id='<env-guid>' only once and the image/environment will continue to be used for subsequent deployments (as long as it isn't overwritten by another deployment). This means that the arguments doesn't need to be provided every time deploy <app> is called, which is how the current --image flag behaves. This is the same workflow used by the Connect dashboard.