Allow conflicting optional dependencies and dependency groups

[zanieb]

A project should be able to declare mutually exclusive optional dependencies, which have conflicting requirements and are solved separately.

This problem is challenging because if any optional dependency group can be incompatible with any other group, we need to perform a resolution for every possible dependency group combination.

Note, following the recent standardization of local dependency groups, this issue includes allowing conflicts in those as well. The underlying changes that need to happen in the resolver are the same.

See also #6729

[WelanderJacob]

We're currently adopting uv in our company and recently encountered this issue. I was wondering if there are any updates or timeline on when this feature might be addressed? It would be really valuable for us.

Anyway, thanks for all the fantastic work on uv!

[zanieb]

We're working on this now, but we consider it a difficult / high risk problem so I'm not sure when we'll have a solution.