Adds ability to filter by category, adds invoice allowance as an account option

src/clj/auto_ap/graphql/sales_orders.clj

@@ -76,6 +76,7 @@
                                 :total_gte  {:type :money}
                                 :type_name  {:type 'String}
                                 :processor  {:type :processor}
+                                :category  {:type 'String}
                                 :start      {:type 'Int}
                                 :per_page   {:type 'Int}
                                 :sort       {:type '(list :sort_item)}}