Feature: Support multiple index urls

[MattiasDC]

Before You Begin

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• [x] I have checked for similar feature requests in the project's issue tracker to avoid duplicates.
• [x] I have searched existing issues to see if this feature has been discussed before.

Feature Details

It's possible to configure both pip and uv to use multiple index urls to search/install packages. This can be done with the --extra-index-url option for example in pip/uv. LicenseCheck currently doesn't support this functionalty, and hence does not find all packages that we want to have checked.

Describe the solution you'd like

The pypi-api configuration option accepts a list of api endpoints

Describe alternatives you've considered

Current workaround is to use the api endpoint containing the most packages, and adding all packages that come from the other index to the ignore list. This is however clearly suboptimal.