Using resource data in ACL Templating

Vault
1

Apologies if I have the terminology incorrect
I am using vault v1.14.2+ent

I am writing a policy to allow a vault user to change their own password
only in userpass.

I have created the following resource

resource "vault_auth_backend" "userpass" {
  type = "userpass"
}

how do I get the userpass accessor value and use it within an ACL Template?

path "authuserpass/users/{{identity.entity.aliases.<auth_userpass_accessor>.name}}" {...

I have tried

{{identity.entity.aliases.{vault_auth_backend.userpass.accessor}.name}}
{{identity.entity.aliases.vault_auth_backend.userpass.accessor.name}}

and while the policy is imported into vault it just shows the original syntax and not the value
of the accessor.

I don’t want to have to hard code the auth_userpass accessor value within the policy, as this code will likely be used to populate the policies on multiple instances of Vault.