Authentication fails with credential-helper registered

When I have a global credential-helper registered, the built-in authentication handling, e.g. temporary tokens, don't work as bazel is stripping them. I asked @Yannic, who told me that in the future the auth attribute will probably be stripped too.

No files, tests, or entry points are named. Start by reproducing authentication with a global credential helper and temporary tokens, then trace the Bazel rules' credential handling; done means built-in authentication works without being stripped when a helper is registered.

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