Groups-based Action Decorator System

[azht]

Summary

Adds groups-based access control for shared agents. Agents can declare which Globus groups may invoke each action via a sharing param on the @action decorator with union semantics across groups. Currently sharing=[] makes an action owner-only, and ommiting it falls back to the union of all groups declared on that agent's actions.

Decisions

• The sender of a message doesn't self report it's group memberships the exchange checks those and stamps messages with relevant group memberships.
• We use the union of all groups with any ability to call any action on an agent for cases where the sharing param is undeclared on an action, and sharing=[] makes it owner only.
• ShutdownRequest is owner-only; CancelRequest is allowed for the owner or the original requester. Agents that declare no sharing anywhere keep the existing open behavior, so this is backwards compatible for agents not using the feature.
• New error code RequestForbiddenError. The header gains a groups field that's default empty so existing messages still validate.

Related Issues

• Closes #324

Changes

• Breaking (backwards incompatible changes to public interfaces) ✅ 2026-07-15
  • Some non-sharing things affected: terminate now requires mailbox ownership, shutdown is owner-only when owner is recorded.
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (non-breaking change or feature addition) ✅ 2026-07-15
• Refactor (internal code or design clean up)
• Documentation (no changes to the code)
• Test (changes or additions to testing) ✅ 2026-07-15
• Build (change to CI workflows or build processes)
• Package (changes to package metadata or dependency versions) ✅ 2026-07-15

Testing

Added test covering: per-action sharing authorization (allow/deny/owner), explicit empty sharing (owner-only), fallback to the agent group union for undecorated (agree with Alok, this preserves past behavior), owner-only shutdown, response delivery to unshared mailboxes, ownership checks in create/termiante/put, owner propagation through agent registration (maybe a few more?). All tests in the touched files pass locally (156 passed).

Pull Request Checklist

Please confirm the PR meets the following requirements.

• Relevant tags are added based on the types of changes.
• Code changes pass pre-commit (e.g., ruff, mypy, etc.). ✅ 2026-07-15
• Tests have been added to show the fix is effective or that the new feature works. ✅ 2026-07-15
• New and existing unit tests pass locally with the changes. ✅ 2026-07-15
• Docs have been updated and reviewed if relevant.