feat: Add package:cedar_ffi (#65)

Adds an FFI-based implementation of the Cedar authorizer using the official Rust implementation.

.github/workflows/cedar_ffi.yaml

@@ -0,0 +1,43 @@
+name: cedar_ffi
+on:
+  pull_request:
+    paths:
+      - ".github/workflows/packages_cedar_ffi.yaml"
+      - "packages/cedar_ffi/**"
+      - "packages/cedar_ffi/third_party/cedar"
+      - "packages/cedar_ffi/third_party/cedar/**"
+
+# Prevent duplicate runs due to Graphite
+# https://graphite.dev/docs/troubleshooting#why-are-my-actions-running-twice
+concurrency:
+  group: ${{ github.repository }}-${{ github.workflow }}-${{ github.ref }}-${{ github.ref == 'refs/heads/main' && github.sha || ''}}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-latest
+          - macos-14
+          - windows-latest
+    runs-on: ${{ matrix.os }}
+    # TODO(dnys1): Speed up Rust builds
+    timeout-minutes: 15
+    steps:
+      - name: Git Checkout
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # 4.1.1
+        with:
+          submodules: true
+      - name: Setup Dart
+        uses: dart-lang/setup-dart@fedb1266e91cf51be2fdb382869461a434b920a3 # main
+      # Will often be out-of-date on runners
+      - name: Setup Rust
+        run: rustup update stable && rustup default stable
+      - name: Get Packages
+        working-directory: packages/cedar_ffi
+        run: dart pub get
+      - name: Test
+        working-directory: packages/cedar_ffi
+        run: dart --enable-experiment=native-assets test --fail-fast

.gitignore

@@ -2,4 +2,12 @@
 .DS_Store
 doc/api/
 **/doc/api/
-pubspec_overrides.yaml
+pubspec_overrides.yaml
+
+## RUST ##
+# will have compiled files and executables
+debug/
+target/
+
+# These are backup files generated by rustfmt
+**/*.rs.bk

.gitmodules

@@ -0,0 +1,4 @@
+[submodule "packages/cedar_ffi/third_party/cedar"]
+	path = packages/cedar_ffi/third_party/cedar
+	url = https://github.com/cedar-policy/cedar
+	branch = release/3.1.x