How can I set a custom figcaption in an attatchment uploded?

## Details
I have been trying to set a custom figcaption in this way

```
attrs["content"]= `



${attachment.file.name}
${attachment.getFormattedFilesize()}
Download
`
```

But for some reason when the it renders it keeps the figcaption generated by trix


How can I add content to that figcaption generated by trix?

No project file, test, or entry point is identified in the issue. Start by reproducing the uploaded-video rendering and trace how Trix generates the attachment figcaption; done would mean documenting or implementing a supported way to add custom figcaption content.

Written by the indexing model from the issue text.