Specify the hashing algorithm for certificate thumbprint in the policy validate-client-certificate

[FlorentATo]

Doc: https://learn.microsoft.com/en-us/azure/api-management/validate-client-certificate-policy The documentation should specify the supported hashing algorithm for the attribute "thumbprint".

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services: api-management author: @dlepow ms.service: azure-api-management ms.topic: article ms.author: @danlep