Potential global name clash with ACR instance in quickstart

[dominicbetts]

In the quickstart to install Azure IoT Operations:

If you let the scripts autogenerate the name of the Azure Container Registry instance, then you're likely to get a global name clash in Azure, as they try to try to create an ACR called iotopsclusteracr which already exists.

As a workaround, make sure to add your own ACR instance name in the config file using the key: container_registry.

[BillmanH]

Fix — Append a short random suffix in the auto-generated name (script change)

In external_configuration/External-Configurator.ps1, replace the current auto-generation block (~line 663–667):

# BEFORE
if (-not $script:ContainerRegistryName) {
    $script:ContainerRegistryName = ($clusterNameClean + "acr").Substring(0, [Math]::Min(50, ($clusterNameClean + "acr").Length))
    $script:ContainerRegistryLoginServer = "$($script:ContainerRegistryName).azurecr.io"
    Write-InfoLog "Using auto-generated container registry name: $script:ContainerRegistryName"
}

# AFTER
if (-not $script:ContainerRegistryName) {
    # Append a 6-char suffix derived from the subscription ID to reduce global name collisions.
    # ACR names: 5-50 chars, alphanumeric only, globally unique.
    $suffix = ($script:SubscriptionId -replace '-', '').Substring(0, 6)
    $baseName = $clusterNameClean + "acr" + $suffix
    $script:ContainerRegistryName = $baseName.Substring(0, [Math]::Min(50, $baseName.Length))
    $script:ContainerRegistryLoginServer = "$($script:ContainerRegistryName).azurecr.io"
    Write-InfoLog "Using auto-generated container registry name: $script:ContainerRegistryName"
}

Using the first 6 characters of the subscription ID (hex, no dashes) makes the name deterministic per-subscription (so re-runs are idempotent) while being unique enough to avoid cross-user collisions.

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[BillmanH]

Addressed in: #190