BASE_URL ignores path component

[nh2]

Bug report

I'm trying to set BASE_URL=https://example.com/plausible, so that the root of Plausible starts at /plausible.

However, it does not work: Plausible redirects to https://example.com/login, outside of the BASE_URL.

I believe this is because Plausible completely ignores the .path component of the parsed URI:

analytics/config/runtime.exs

Line 181 in 145a359

url: [host: base_url.host, scheme: base_url.scheme, port: base_url.port],

Expected behavior

Plausible should respect the path component of the BASE_URL, so that it can run under a path that is not the domain root.

In #177 it was mentioned that Plausible strips query parameters after ?, but nowhere is it mentioned that it strips the /path, so I assume that this is accidental.