nightlies and link validation failing because of repository.apache.org blockage

Our nightlies and link validation sometimes fail when it is ran on a GitHub Actions running that is blocked from repository.apache.org.

Infra seems open to create per-project buckets for the abuse thresholds, but we'd have to add a header to the requests to identify ourselves.

Looks like this would depend on https://github.com/coursier/coursier/issues/1203

Start by locating the GitHub Actions workflows for nightlies and link validation, then read coursier issue 1203 and trace their requests to repository.apache.org. Done means the workflows identify the project with the required header and no longer fail solely because of repository.apache.org blocking.

Written by the indexing model from the issue text.