As part of the Azure App Service Certificate offering, we support Web Apps certificate deployment through Azure Key Vault.
App Service Certificate stores the private certificate into a user-provided Key Vault secret. When App Service Certificate is deployed into a web app, a Web Apps resource provider deploys it from the Key Vault secret that's associated with App Service Certificate.
Essentially, App Service Certificate and Web Apps are loosely connected through Key Vault. If you manually upload a private certificate into a Key Vault secret, you can use the same feature for deploying your own certificate into Web Apps through Key Vault.
For more information, see the full blog post.