feat(agent): support canceling package broker operations

[Vladyslav Nikonov (vnikonov-devolutions)]

Adds a POST /v1/package-operations/cancel endpoint to the Devolutions Agent package broker. Clients can now cancel an in-flight package operation: the broker terminates the spawned package-manager process and reports the operation as Canceled. Cancelation is idempotent, and canceling an already-finished operation simply returns its final status. Unknown operations, or operations owned by another client, are reported as not found.

This enables UniGetUI (and other broker clients) to give users a working cancel button for installs, updates, and uninstalls that run through the broker.

Depends on now-policy-api / now-policy-server-template 0.3 (cancel API, Canceling/Canceled statuses, API version 1.1).

Note

Draft: the workspace Cargo.toml temporarily patches now-policy-api and now-policy-server-template to a local path. These patches must be removed once the 0.3 crates are published to crates.io.

[Vladyslav Nikonov (vnikonov-devolutions)]

Implementation notes:

• New endpoint: POST /v1/package-operations/cancel (CancelRequest/CancelResponse from now-policy-api 0.3). Auth mirrors the status endpoint: client context + Devolutions Authenticode signature validation, plus an owner-key check (effective_user|client_executable_path), so a client can only cancel its own operations (NotFound otherwise).
• Cancel semantics: async + idempotent. A non-terminal operation transitions to Canceling and its per-operation CancellationToken (stored in OperationTracker) is triggered; the response reports Canceling. Terminal operations return their final status unchanged. Repeated cancels are harmless.
• Process termination: the Windows executor's create_process wait was changed from a single 1-hour blocking wait to a 500 ms polling loop that checks the cancel token and the overall deadline. On cancel it terminates the process (exit code 1) and returns a typed ExecutionCanceled error; the background execution task downcasts it and marks the operation Canceled instead of Failed.
• Token plumbing: the cancel token only guards the pre-command and the main command; kill-before-operation and post-operation commands get a fresh token (post is best-effort cleanup and is skipped anyway when the main command errors out).
• Race handling: mark_running refuses to regress Canceling/Canceled; mark_completed/mark_failed never overwrite Canceled. If a process exits normally before the terminate lands, its real outcome wins.
• Testing: unit tests cover unknown-operation, running-operation (token fired + Canceling), terminal-operation (status preserved), and owner-mismatch paths, plus tracker state-transition guards. cargo +nightly fmt, cargo clippy --tests -D warnings, and cargo test -p devolutions-agent all pass.
• Temporary: [patch.crates-io] path entries for now-policy-api/now-policy-server-template point at a local now-proto worktree until 0.3 is published; remove before merging (marked with a TODO).

[github-actions]

Let maintainers know that an action is required on their side

• Add the label release-required Please cut a new release (Devolutions Gateway, Devolutions Agent, Jetsocat, PowerShell module) when you request a maintainer to cut a new release (Devolutions Gateway, Devolutions Agent, Jetsocat, PowerShell module)

• Add the label release-blocker Follow-up is required before cutting a new release if a follow-up is required before cutting a new release

• Add the label publish-required Please publish libraries (`Devolutions.Gateway.Utils`, OpenAPI clients, etc) when you request a maintainer to publish libraries (Devolutions.Gateway.Utils, OpenAPI clients, etc.)

• Add the label publish-blocker Follow-up is required before publishing libraries if a follow-up is required before publishing libraries