Add jsonDumps default option to SaratogoAPI ...

object to perform textualisation of non-text/number objects

Perfectly understand if this is too crude to include at such a high level.

example:
<pre>
    def _todate(obj):
        return obj.strftime('%d/%m/%Y')

    api = SaratogaAPI(DKIM, DKIM_APIDef, serviceClass=Database(), jsonDumpsDefault=_todate)

</pre>