Add account entity token support (balance_amount); factories + feature test

app/Services/Documents/TokenValueResolver.php

@@ -78,6 +78,9 @@ private function entityAttribute(string $entity, string $attr, Contract $contrac
                 $person = optional(optional($contract->clientCase)->person);
 
                 return (string) $person->{$attr};
+            case 'account':
+                $account = optional($contract->account);
+                return (string) $account->{$attr};
             default:
                 return '';
         }