Given subscription key - how to find associated user?

@Martin Kallukalam Here is sample script where it checks all the apim instances within your subscription to identify the respective subscription Id and user who owns it. Kindly fill in the respective values where "xxx" is mentioned.

try {
    "Logging in to Azure..."
    Connect-AzAccount  -Tenant "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxx" 
}
catch {
    Write-Error -Message $_.Exception
    throw $_.Exception
}

    
$subscriptions = Get-AzSubscription -SubscriptionId "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxx"

Set-AzContext -Subscription $subscriptions[0]

$apiminstances = Get-AzApiManagement

foreach (  $apim in $apiminstances) {
    $apimContext = New-AzApiManagementContext -ResourceGroupName $apim.ResourceGroupName -ServiceName $apim.Name
    $sId = Get-AzApiManagementSubscription -Context $apimContext

    foreach ($s in $sId) {
        $subKey = Get-AzApiManagementSubscriptionKey -Context $apimContext -SubscriptionId $s.SubscriptionId 
        if ($subKey.PrimaryKey -eq "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx" -or $subKey.SecondaryKey -eq "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx") {
            $subtemp = Get-AzApiManagementSubscription -context $apimContext -SubscriptionId $s.SubscriptionId
            $user = Get-AzApiManagementUser -Context $apimContext -UserId $subtemp.UserId
            Write-Host "Subscription ID: " + $s.SubscriptionId + " User ID: " + $user.Id + " User Email: " + $user.Email
        }
    }
}