Client support for Rekor V2: sigstore-python #289

Addresses #1413

Summary

Runs tests against local rekor and fulcio containers using the sigstore/scaffolding setup-sigstore-env Action.

• Adds a new workflow .github/workflows/test-with-setup-sigstore-env.yml that runs scaffolding/setup-sigstore-env for local sigstore service containers.
• Renames the staging fixture preprod
• parameterizes the preoprod fixture to also support a new "local" option that uses the local containers.
  • if the conditions in .github/workflows/test-with-setup-sigstore-env.yml are not met, then test insstances that would use use the local containers are skipped.
  • see https://docs.pytest.org/en/stable/how-to/fixtures.html#fixture-parametrize

TODO:

• Add the option to more tests
• Consider adding this to the staging fixture, which may need renaming to perhaps "preprod". We would paramaterize the fixture, so that every test function that uses the fixture would automatically run twice: once for real staging rekorv1 and again for alpha rekor v2.
• make verification work for the local containers. It seems like an issue verifying the local fulcio certificate chain.
• fix problem where lots of tests are skipped within CI.
  • Tests are skipped in this PR because my PR is from a fork, and so will not have permissions for id-token: write. I think a maintainer needs to close and reopen this PR for it work work, or open another PR from my branch.
    • SKIPPED [33] test/conftest.py:104: skipping test that requires an ambient OIDC credential
  • They are actually working on another PR in my fork repo.
    • Test with setup-sigstore-env Action #1441
    • https://github.com/ramonpetgrave64/sigstore-python/actions/runs/15643987379/job/44077716123#step:6:25

Release Note

Documentation