Azure Function Url doesn't include authentication code when using azurerm_runction_app_function

When you setup a Function in Azure, it lets you get the default function Url with the function key. It looks sort of like:[authentication-code]

This lets me call that function from an API endpoint without using any other authentication. I am trying to get access to that key via the azurerm provider somehow. I can get the main Url (not including the authentication code) using I can get the host key using data.azurerm_function_app_host_keys.default_function_key. But I can’t seem to find anything that gives me the default function key for my specific function, as is available in the Azure portal. Please help.