you can't add an existing invoice.

src/clj/auto_ap/graphql/invoices.clj

@@ -13,6 +13,10 @@
     (vendors/insert {:name vendor-name :default-expense-account 0})))
 
 (defn add-invoice [context {{:keys [total invoice_number location company_id vendor_id vendor_name date] :as in} :invoice} value]
+  (when (seq (invoices/find-conflicting {:invoice-number invoice_number
+                                         :vendor-id vendor_id
+                                         :company-id company_id}))
+    (throw (ex-info "that invoice already exists" {:invoice-number invoice_number})))
   (let [vendor (-create-or-get-vendor vendor_id vendor_name)
         _ (assert-can-see-company (:id context) company_id)
         company (companies/get-by-id company_id)