how to add a functionapp slot identity to a postgresql database

Question

I would like to add a functionapp slot identity as a user in the database.

However, "SELECT * FROM pgaadauth_create_principal('functionappname/slot/slotname', false, false);" fails with an unexpected error.

The following message is provided: SQL statement "SECURITY LABEL for "pgaadauth" on role "appname/slot/slotname" is 'aadauth'"