Automatically attach an additional file to Send Invoice Reminder, Email or Support Ticket through API or Hooks

[GKey]

Greetings,

In our current setup, after invoice reminders are sent, we are sending additional Files to the users containing more detailed information about their usage of our services.
At the moment, we are forced to do this manually - by creating a custom email or support ticket and manually attaching files to it.

I am looking for ways to automate this process and eliminate the need for manual actions.

The ideal situation would be to send an additional file in the same email as the Invoice Reminder is sent, if specific criteria is met (which will be set in the code). The files could be located in the in a local directory or in User Profile's File department, both are fine.
This could be achieved through Invoice Payment Reminder Hook. However, I am unsure what is the actual syntax/variable names etc to actually attach the second file.
The current documentation does not mention this anywhere.

The workaround would be to call API commands through Invoice Payment Reminder Hook, specifically SendMail and send a separate email with the attachement. While this is more self explanatory, again the documentation does not mention anything about Attachments.

Could some please clarify how to do the email attachements through API or Send Invoice Reminder Hook ?

Thank you in advance,

GKey