Create a setting to allow delayed billing for ACH

[shaneonabike]

Problem

We have created a Contribution form that provides special options for delayed billing besides what's actually out-of-the-box (like Quarterly, etc).

When submitting the form it fails due to the code below (from iATS.php in iats_civicrm_pre

      // Fix a civi bug while I'm here.
      if (empty($params['installments'])) {
        $params['installments'] = '0';
      }

What I expect

Maybe a setting in iATS to be able to turn this off and on?

Proposed Solution

Would it be possible that we could provide a setting in iATS settings page that either turns this off an on. I'd rather not have to hotpatch this each time.

If you have some specific preferred I'm happy to create a patch to contribute. I was thinking like Set default instalments to zero, although I'm sure there is better. Then out of the box it could be set to true.