How do I get attachment names from multiple issues with smart values

[David Meadow]

I have an automation rule that works across all the issues linked to an epic. We are sending issue details to an external process via webhook. Using {{#issues}}{{key}}, {{/}} in the body of the web request I get a comma separated list of all the keys. If I run {{attachment.filename}} against ONE issue (different rule to test the smart value) I get a comma separated list of the attachments for that issue. What I would really like is a list of all the issue keys linked to the epic, and all the attachments associated with those issues. They don't even have to be associated pairs, I just need the values. I tried variations of:

{#issues}}{{key}}{{attachment.filename}}, {{/}}

{#issues}}{{key}}, {{attachment.filename}}, {{/}}

{#issues}}{{key}} {{#attachments}}{{filename}}, {{/}}

{#issues}}{{key}} {{/}}, {{#attachments}}{{filename}}, {{/}}

...

and to attempt just the file names:

{{attachment.filename}}

{#attachments}}{{filename}}, {{/}}

etc.

the best I got was a list of issue keys followed by a string of commas and spaces.