added new invoices_xf model

models/transform/quickbooks_invoices_xf.sql

@@ -0,0 +1,32 @@
+with invoices as (
+
+    select * from {{ref('quickbooks_invoices')}}
+
+),
+
+payments as (
+
+    select
+        *,
+        total_amt - balance as amount_paid,
+        case
+            when balance < .05 * total_amt then 1
+            else 0
+        end as paid
+    from invoices
+
+),
+
+final as (
+
+    select
+        *,
+        case
+            when paid = 0 and due_date < current_date then 1
+            else 0
+        end as overdue
+    from payments
+
+)
+
+select * from final