[payments] Add VAT to the gross amount to ensure accounts page in SDK has matching values to the customer portal and invoice. (#829)

Author: bahiirwa

includes/entities/class-fs-payment.php

@@ -132,10 +132,11 @@ function is_migrated() {
          */
         function formatted_gross()
         {
+            $price = $this->gross + $this->vat;
             return (
-                ( $this->gross < 0 ? '-' : '' ) .
+                ( $price < 0 ? '-' : '' ) .
                 $this->get_symbol() .
-                number_format( abs( $this->gross ), 2, '.', ',' ) . ' ' .
+                number_format( abs( $price ), 2, '.', ',' ) . ' ' .
                 strtoupper( $this->currency )
             );
         }