How to set primary identity: user assigned managed identity for azurerm_mssql_server

Hi Everyone,
-So i have written a code where I have created a SQL server and assigned a user assigned managed identity to it.
-The next step I am taking is data encryption, in order to do that, I need to have a primary identity in the “identity” section.

  • How can I specify a primary identity in the terraform code???

i know that in the documentation terraform says we can only use systemassigned, so does that mean user assigned doesnt have those full functionality yet?