feat(jans-cedarling): add C bindings support

[haileyesus2433]

Prepare

• Read PR guidelines
• Read license information

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Description

Target issue

closes #11754

Implementation Details

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Test and Document the changes

• Static code analysis has been run locally and issues have been fixed
• Relevant unit and integration tests have been added/updated
• Relevant documentation has been updated if any (i.e. user guides, installation and configuration guides, technical design docs etc)

Please check the below before submitting your PR. The PR will not be merged if there are no commits that start with docs: to indicate documentation changes or if the below checklist is not selected.

• I confirm that there is no impact on the docs due to the code changes in this PR.

Summary by CodeRabbit

• New Features

  • C bindings packaged as shared/static libraries exposing init, instance lifecycle, authorization (unsigned & multi‑issuer), context data API, logging, trusted‑issuer inspection, error/ memory helpers, and example programs.

• Documentation

  • New C getting‑started tutorial, integrated C snippets in the main guide, and a dedicated C bindings README.

• Tests

  • End‑to‑end C test suite, example Makefiles, and runnable C examples.

• Chores

  • CI updated to add C test job and minor CI formatting fix.

[mo-auto]

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📝 Walkthrough

Walkthrough

Adds a new Cedarling C bindings crate (cdylib/staticlib) with generated C headers, extensive C FFI exports, examples, tests, docs/tutorial pages, and a CI c_tests job; also fixes a trailing-newline artifact in the existing CI workflow.

Changes

Cohort / File(s)	Summary
CI Workflow \.github/workflows/test-cedarling.yml	Adds a top-level c_tests job (checkout with runner hardening, install protoc, install stable Rust, cache Rust workspace, install pinned cbindgen, build cedarling_c release, verify target/include/cedarling_c.h, run C tests with LD_LIBRARY_PATH), and adds a trailing newline to golang_tests.
C Bindings Crate & Build jans-cedarling/bindings/cedarling_c/Cargo.toml, .../build.rs, .../cbindgen.toml	New crate manifest (cdylib/staticlib) with deps and build-dep on cbindgen; build.rs generates header to target/include/; cbindgen.toml configures exported symbols, naming, must-use, and OS preprocessor defines.
FFI Core: types & interface jans-cedarling/bindings/cedarling_c/src/types.rs, .../c_interface.rs, .../lib.rs	Adds C-ABI types (error codes, result structs, string-array), thread-local last-error, helpers to convert/allocate C strings, a process-wide instance registry, ~25+ extern "C" exports covering runtime/instance lifecycle, authorization, context data API, logging, trusted-issuer inspection, and memory utilities.
Examples & Makefiles jans-cedarling/bindings/cedarling_c/examples/basic_example.c, .../authorize_unsigned.c, .../authorize_multi_issuer.c, jans-cedarling/bindings/cedarling_c/examples/makefile	Adds three C example programs demonstrating init/instance/authorize/log retrieval/cleanup and a Makefile supporting dynamic/static linking, platform libs, run targets, and rpath/LD_LIBRARY_PATH handling.
Tests & Test Makefile jans-cedarling/bindings/cedarling_c/tests/test_cedarling.c, jans-cedarling/bindings/cedarling_c/tests/makefile	Adds an end-to-end C test harness covering success/error paths, context API, logging, trusted-issuer queries, memory utilities, lifecycle, plus a Makefile to build/run tests with rpath/LD_LIBRARY_PATH handling.
Documentation & Navigation docs/cedarling/tutorials/c.md, docs/cedarling/tutorials/cedarling-getting-started.md, jans-cedarling/bindings/cedarling_c/README.md, mkdocs.yml	Adds comprehensive C bindings tutorial and examples, augments getting-started with a C tab, introduces crate README/API reference, and inserts the C tutorial into mkdocs navigation.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

Possibly related PRs

• feat(jans-cedarling): add authorize_multi_issuer to bindings #12431 — Adds/exposes authorize_multi_issuer binding APIs across language bindings; directly overlaps the new C multi-issuer API.
• feat(jans-cedarling): update bindings to include the new context data interface #13173 — Adds the Context Data API surface across bindings; directly related to the cedarling_context_* C FFI functions.
• ci: fix missing toolchain #13250 — Modifies the same CI workflow and Rust toolchain/CI setup; overlaps with the .github/workflows/test-cedarling.yml changes.

Suggested reviewers

• dagregi
• moabu

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'feat(jans-cedarling): add C bindings support' clearly and concisely summarizes the main change—adding C bindings to Cedarling to enable C developers to use the authorization engine.
Description check	✅ Passed	The PR description follows the required template, includes the target issue (#11754), confirms code analysis was run, documents that tests were added/updated, confirms documentation was updated, and indicates no doc impact.
Linked Issues check	✅ Passed	The PR fully addresses the linked issue #11754 objective by providing a complete C-compatible API that exposes Cedarling functionality to C applications through FFI bindings, runtime management, authorization APIs, context data management, and logging functions.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to adding C bindings support: Rust FFI layer, C examples, build configuration, CI/CD test automation, and corresponding documentation. No unrelated refactoring or feature creep is present.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch jans-cedarling-11754

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[haileyesus2433]

the failing C tests will be resolved once #13538 is merged its currently blocked by that

[tareknaser]

Thank you for the great work so far. I left a couple of final commits.

[tareknaser]

Thank you for the great work. I have no further comments

[haileyesus2433]

@coderabbitai could u please approve if u dont have any suggestions

[coderabbitai]

Tip

For best results, initiate chat on the files or code changes.

@haileyesus2433, thanks for reaching out! A couple of things to note:

1. Approval command: To trigger an approval from me, you need to post @coderabbitai approve as a top-level PR comment (not a reply in a thread).

2. Outstanding items before approval: There are a couple of things still pending on this PR that I'd recommend addressing first:

   • Failing C tests: You've noted these are blocked by PR #13538. It would be best to get that merged and confirm CI is green before approval.
   • Pending human review: @tareknaser has indicated they have review comments in progress and plan to submit their review in the next couple of days. It would be good to wait for and address their feedback first.

Once the dependent PR is merged, CI passes, and the human reviewer's feedback is addressed, feel free to post @coderabbitai approve as a top-level comment and I'll take another look!

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🧠 Learnings used

Learnt from: olehbozhok
Repo: JanssenProject/jans PR: 13173
File: jans-cedarling/bindings/cedarling_python/src/context_data_api/data_entry.rs:12-34
Timestamp: 2026-02-04T20:09:55.585Z
Learning: In jans-cedarling Python bindings (jans-cedarling/bindings/cedarling_python/**/*.rs), Python-style documentation with explicit sections like "Attributes" and Python type hints is acceptable because these bindings expose Rust to Python consumers who benefit from Python-style documentation conventions.

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Learnt from: olehbozhok
Repo: JanssenProject/jans PR: 13173
File: jans-cedarling/bindings/cedarling_python/src/context_data_api/data_store_stats.rs:9-33
Timestamp: 2026-02-04T20:10:06.440Z
Learning: In jans-cedarling Python bindings (jans-cedarling/bindings/cedarling_python/**/*.rs), Python-style documentation with explicit sections like "Attributes" and detailed field descriptions is acceptable and preferred because these bindings expose Rust to Python consumers who benefit from Python-style documentation conventions.

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Learnt from: olehbozhok
Repo: JanssenProject/jans PR: 12903
File: jans-cedarling/bindings/cedarling_wasm/src/lib.rs:83-97
Timestamp: 2025-12-26T17:33:20.543Z
Learning: In jans-cedarling WASM bindings (jans-cedarling/bindings/cedarling_wasm/**/*.rs), explicit documentation sections like `# Arguments` and `# Example` are acceptable because these bindings expose Rust to JavaScript consumers who benefit from more explicit parameter documentation and JavaScript usage examples.

[haileyesus2433]

Thank you for the great work. I have no further comments

thank you verymuch for the reviews

[haileyesus2433]

@coderabbitai approve

[coderabbitai]

✅ Actions performed

Comments resolved and changes approved.