Add Azure KeyVault support for managing secrets in Keyvault with Java

[SharePointing]

1. Setting up of azure key vault connection using certificate or service principal with certificate for additional security.
2. Referencing Key Vault secrets/props via Azure App Service’s Application settings. The documentation https://docs.microsoft.com/en-us/azure/app-service/app-service-key-vault-references doesn’t give step by step guide.

• This would allow us to show Java / Spring developers how to do this the right way.