Right now the insight notification emails go out after 4am in the installation's timezone.
In 7a8f9b5 I added a timezone field to the owners table, which gets set to the installation's TZ by default, but the user can change it in their settings.
Let's send the email at 4am in the local time of the owner's timezone versus the installations (Config's) timezone setting.
Send insight notification emails in owner-specific timezone
Closes #1792, closes #1790