Taxonomy containing a locale string breaks taxonomy_list links

[BenjaminAndre]

Bug Report

Environment

Zola version: 0.19.2

Expected Behavior

If I write (in a template but probably in most places)

<a href="{{ get_url(path='genres', lang=lang) }}">
	Genres
</a>

I expect the French (main language) to link to root/genres, and the English secondary language to link to root/en/genres

Current Behavior

The English version leads also to root/genres just like the French version. Which, for the user, looks like he falls back to French.

Step to reproduce

Since my other taxonomies (tags and authors) don't have the same problem and I investigated a little, I suspect it's the en in the taxonomy (genres) that causes the problem.
I'd bet it messes up a regex somewhere in the get_url macro.

[Keats]

It looks like lots of people (#2598) are confused about get_url so it should probably be changed.

Here's a short version of what it does: #2598 (comment)

It should probably be split into several functions rather than one function searching through many things.

[brianmay]

When even the docs are confused about what get_url can do (see https://www.getzola.org/documentation/content/image-processing/#creating-picture-galleries) it is not surprising users are confused also.

There probably does need to be a way of mapping an internal path to an external URL. i.e. just like get_link(path="@/...") but works with more then just md files. And probably without requiring string concatenation.