Slack `files.completeUploadExternal` method uses string instead of object for `files` property

[jonnilundy]

1. My goal: I'm building a daily reporting workflow and I want to create a graph using chart.js and then upload that to Slack.
2. Issue: On the last step of the flow, I need to hit the files.completeUploadExternal slack method and pass an object on the files` property. Unfortunately, the property is set to be a string and I don't see a way to override it. This results in a failed step and no way to finish uploading a file to Slack.
3. Steps I've taken to troubleshoot: I've tried changing the format to a json instead of a string.
4. Additional info: Cloud

[Darren]

Hmm there is something wonky with this. Thanks for reaching out, @jonnilundy. It looks like the template string isn't being correctly interpolated, but a quick and easy fix is to just wrap it in double quotes.

That should hopefully unblock you, but I'll reach out internally to see if we can get this fixed.

[jonnilundy]

Thanks for the quick help, Darren. That workaround unblocked me, definitely strange though.