Download Report API: Add path to response, fix ordering, and fix schema typo

[justinshreve]

Fixes #1245.

This PR fixes a few issues with the download report endpoints.

• It adds a download_path to the response which contains a URL to the download of the file.
• It fixes a typo between download_count and downloads_count in the schema.
• It fixes the ?orderby option so it actually sorts. Tests included.

Note on download_path:
This links to the file path that is stored in the product data. This can link externally or to the media library. It is different from a WC download link. Download links are tied to orders/users, so to use that we would need to generate permissions for each admin and link here otherwise.

Detailed test instructions:

• Running phpunit should be enough to test the changes here, though you can make manual requests or test the report page as well.

[Aljullu]

This is looking good to me.

Probably that's outside of the scope of this PR, but I couldn't see match: any behaving differently than match: all.

Using match: any with a downloadIp_includes that matches one download but a user_includes that doesn't match any, returns 0 results while I would expect it to return 1. Am I missing something or is there a bug here?

[justinshreve]

Sounds like a bug - I'll take a look in a follow-up PR!