Enable the uv pep621 manager for Python work with dependencies in private registries

[torarvid]

Tell us more.

Today, the uv manager works well as long as all dependencies in a repo are hosted publicly. However, for a repo that has one or more dependencies that are private, Renovate will fail to generate working PRs, since the step to update the lockfile uv.lock will fail.

This lock step is done by invoking uv lock, and by default uv will only be able to discover dependency information directly from pypi.

I've made an example repo here: https://github.com/torarvid/renovate-test. It has configuration keys for packageRules to tell it the URL to my private registry, and hostRules to give it credentials to said registry.

When I clone the renovate repository and run it against this test repo, it generates a PR such as this one: torarvid/renovate-test#3 where the Renovate comment says Command failed: uv lock --upgrade-package private-torarvid-package-1.

I tried digging into this a little bit, and while I'm no expert on the inner workings of Renovate, it seems to me that this could be improved by matching the registryUrl with the hostRule and create a URL that can be exported to the env var UV_EXTRA_INDEX_URL which uv will recognize.

I made a proof-of-concept PR here: #31840, and when I run against the same repo it then creates a working Renovate PR like this one: torarvid/renovate-test#9.

I'm aware that I could have discussed this topic here before starting to implement anything, but I just got curious and started poking around. Having said that, I'm in no way "heavily invested" in my PR, so feel free to critique it as you will 😄