BIG-9: fix estimates sorting by customer column.

BIG-10: fix invoices sorting by balance column.

client/src/containers/Sales/Invoices/InvoicesLanding/components.js

@@ -189,11 +189,9 @@ export function useInvoicesTableColumns() {
         clickable: true,
       },
       {
-        id: 'balance',
+        id: 'amount',
         Header: intl.get('balance'),
-        accessor: (r) => (
-          <Money amount={r.balance} currency={r.currency_code} />
-        ),
+        accessor: 'formatted_amount',
         width: 120,
         className: 'balance',
         clickable: true,

server/src/models/SaleEstimate.js

@@ -171,12 +171,12 @@ export default class SaleEstimate extends mixin(TenantModel, [
    */
   static get relationMappings() {
     const ItemEntry = require('models/ItemEntry');
-    const Contact = require('models/Contact');
+    const Customer = require('models/Customer');
 
     return {
       customer: {
         relation: Model.BelongsToOneRelation,
-        modelClass: Contact.default,
+        modelClass: Customer.default,
         join: {
           from: 'sales_estimates.customerId',
           to: 'contacts.id',