InvoiceShelf: Public EmailLog token type confusion allows cross-company invoice disclosure

InvoiceShelf is an open-source web & mobile app that helps track expenses, payments and create professional invoices and estimates. Prior to version 2.4.0, InvoiceShelf public customer invoice, estimate, and payment routes use an EmailLog token's numeric mailable_id without verifying mailable_type, and the JSON handlers do not enforce EmailLog::isExpired. A token issued for one document type can therefore disclose a different company's document when numeric identifiers collide, and an expired token can remain usable on the JSON routes GET /customer/invoices/{email_log:token}, GET /customer/estimates/{email_log:token}, and GET /customer/payments/{email_log:token}. View handlers can also mark a mismatched invoice or estimate as viewed and send a notification. This issue is fixed in version 2.4.0.