Ability to trade multiple cards at once (#360)

- Add the ability to trade multiple cards at once using an optional quantity field

#338

Reviewed-on: #360
Reviewed-by: VylpesTester <tester@vylpes.com>
Co-authored-by: Ethan Lane <ethan@vylpes.com>
Co-committed-by: Ethan Lane <ethan@vylpes.com>

src/database/entities/app/Inventory.ts

@@ -35,6 +35,10 @@ export default class Inventory extends AppBaseEntity {
         this.Quantity -= amount;
     }
 
+    public AddQuantity(amount: number) {
+        this.Quantity += amount;
+    }
+
     public AddClaim(claim: Claim) {
         this.Claims.push(claim);
     }