Track Downloads through Plausible

[tpendragon]

These should be the downloads that go through the "Downloads" controller.

Acceptance Criteria

• [ ] When I go to https://plausible.io/dpul.princeton.edu (or some filter of it) I see a downloads stat that includes all the downloads that went through Figgy's download controller that originated from DPUL-C.
• [ ] There is some way to show all the downloads that went through Figgy's downloads controller regardless of their origin. In this view you can filter by origin site.

Notes

We want Figgy to send the data to DPUL's Plausible for this.

We might be able to get this via https://plausible.io/docs/file-downloads-tracking

We might want to track this through the buttons, or we might get this one for free through #6378.

https://plausible.io/docs/subdomain-hostname-filter#how-to-track-the-user-journey-across-domain-and-subdomains has some useful docs.

We either need a way to measure where the downloads are coming from via some tag manipulation, or have a custom metric we send to the API with some parameters and filter from those.

Answering the questions in these notes will take some research, which is part of this ticket.

First Step

Look at the downloads tracking documentation and see if it'll help.

[tpendragon]

File download tracking didn't work (I guess it doesn't interface with javascript), and neither did outbound link tracking.