Add Azure Key Vault integration

[RomanovM]

nopCommerce version: 4.60

Summary about azure key vault
Secrets Management: Azure Key Vault can be used to securely store and tightly control access to tokens, passwords, certificates, API keys, and other secrets.

Key Management: It provides a secure location to store and manage cryptographic keys. Keys stored in Azure Key Vault are protected by hardware security modules (HSMs). The service supports multiple key types and algorithms, and allows for the creation, import, and control of keys.

Source: https://www.nopcommerce.com/boards/topic/98931/connectionstring-and-secrets-should-use-user-secrets-and-keyvault