AzureKeyVaultSecretsHealthCheck shouldn't return Healthy when a Key Vault has been soft deleted

[eerhardt]

Please, fill the following sections to help us fix the issue

What happened:

The keyvault we were health checking got "soft deleted", but the health check still returns "Healthy"

What you expected to happen:

I expect the health check should return "Unhealthy" in this case

How to reproduce it (as minimally and precisely as possible):

1. Create a key vault
2. Soft delete it
3. Use the AzureKeyVaultSecretsHealthCheck and check the health

Source code sample:

using Azure.Identity;
using Azure.Security.KeyVault.Secrets;
using HealthChecks.Azure.KeyVault.Secrets;
using Microsoft.Extensions.Diagnostics.HealthChecks;

SecretClient client = new SecretClient(new Uri("https://aspiretests.vault.azure.net/"), new DefaultAzureCredential());
AzureKeyVaultSecretsHealthCheck c = new AzureKeyVaultSecretsHealthCheck(client, new AzureKeyVaultSecretsHealthCheckOptions());
HealthCheckResult result = await c.CheckHealthAsync(new HealthCheckContext());

Console.WriteLine(result.Status);

Anything else we need to know?:

AspNetCore.Diagnostics.HealthChecks/src/HealthChecks.Azure.KeyVault.Secrets/AzureKeyVaultSecretsHealthCheck.cs

Lines 48 to 59 in 65ab619

	catch (RequestFailedException azureEx) when (azureEx.Status == 404) // based on https://github.com/Azure/azure-sdk-for-net/blob/main/sdk/core/Azure.Core/README.md#reporting-errors-requestfailedexception
	{
	if (_options.CreateWhenNotFound)
	{
	// When this call fails, the exception is caught by upper layer.
	// From https://learn.microsoft.com/aspnet/core/host-and-deploy/health-checks#create-health-checks:
	// "If CheckHealthAsync throws an exception during the check, a new HealthReportEntry is returned with its HealthReportEntry.Status set to the FailureStatus."
	await _secretClient.SetSecretAsync(name: secretName, value: secretName, cancellationToken).ConfigureAwait(false);
	}
	// The secret was not found, but it's fine as all we care about is whether it's possible to connect.
	return new HealthCheckResult(HealthStatus.Healthy);

This code needs to change to also check for ErrorCode VaultNotFound.

Environment:

• .NET Core version
• Healthchecks version
• Operative system:
• Others: