Log attachments

[soup-bowl]

The current log scrapes emails and their headers, but discards storing their attachments. This is a fundamental feature for sites such as WooCommerce shops that would be dispatching receipt, invoice and/or products via attachments. Currently if an email needs to be resent with attachments, it would need to be re-processed.

There exists a warning on the installation page to inform a potential user that this is not implemented, but I'm leaving this ticket here as a reminder to... Well, actually implement it.