chore: add SBOM release workflow and ADRs

.github/workflows/sbom.yml

@@ -0,0 +1,93 @@
+name: Generate SBOM
+
+# Runs on tag pushes matching the vX.Y.Z pattern.
+# This generates and attaches the SPDX SBOM asset to the GitHub release.
+# It is idempotent: if the SBOM asset already exists for the tag, it is
+# overwritten with the fresh scan output.
+on:
+  push:
+    tags:
+      - "v*"
+
+permissions:
+  contents: write
+  pull-requests: read
+
+concurrency:
+  group: sbom-${{ github.ref }}
+  cancel-in-progress: false
+
+jobs:
+  generate-sbom:
+    name: Generate and Attach SBOM
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+
+      - name: Install Syft (pinned version)
+        run: |
+          curl -sSfL https://raw.githubusercontent.com/anchore/syft/v$SYFT_VERSION/install.sh | sh -s -- -b /usr/local/bin
+
+      - name: Generate SBOM (SPDX format)
+        # Scan the project directory and output an SPDX SBOM file.
+        env:
+          SYFT_VERSION: 'v1.41.0'
+        run: |
+          syft . -o spdx-json=sbom.spdx.json
+
+      - name: Find release ID for the pushed tag
+        id: release
+        run: |
+          TAG_NAME="${GITHUB_REF#refs/tags/}"
+          # Query the GitHub API for a release with this tag name
+          RELEASE_ID=$(curl -s -H "Authorization: token $GITHUB_TOKEN" \
+            "https://api.github.com/repos/${GITHUB_REPOSITORY}/releases/tags/$TAG_NAME" \
+            | jq -r '.id')
+
+          if [ -z "$RELEASE_ID" ] || [ "$RELEASE_ID" = "null" ]; then
+            echo "release_id=" >> "$GITHUB_OUTPUT"
+          else
+            echo "release_id=$RELEASE_ID" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Check for existing SBOM asset and upload
+        if: steps.release.outputs.release_id != '' && steps.release.outputs.release_id != 'null'
+        run: |
+          RELEASE_ID="${{ steps.release.outputs.release_id }}"
+
+          # Check if an SBOM asset with this name already exists in the release
+          ASSET_ID=$(curl -s -H "Authorization: token $GITHUB_TOKEN" \
+            "https://api.github.com/repos/${GITHUB_REPOSITORY}/releases/${RELEASE_ID}/assets" \
+            | jq -r ".[] | select(.name == \"sbom.spdx.json\") | .id")
+
+          if [ -n "$ASSET_ID" ] && [ "$ASSET_ID" != "null" ]; then
+            # Delete existing SBOM asset so we can re-upload the fresh scan
+            curl -s -X DELETE -H "Authorization: token $GITHUB_TOKEN" \
+              "https://api.github.com/repos/${GITHUB_REPOSITORY}/releases/assets/$ASSET_ID" > /dev/null
+            echo "Deleted existing sbom.spdx.json asset"
+          fi
+
+          # Upload the SBOM as a release asset
+          curl -s -X POST -H "Authorization: token $GITHUB_TOKEN" \
+            -H "Content-Type: application/spdx+json" \
+            --data-binary @sbom.spdx.json \
+            "https://uploads.github.com/repos/${GITHUB_REPOSITORY}/releases/${RELEASE_ID}/assets" > /dev/null
+          echo "Uploaded sbom.spdx.json to release $RELEASE_ID"
+
+      - name: Notify if no release found for tag
+        if: steps.release.outputs.release_id == '' || steps.release.outputs.release_id == 'null'
+        run: |
+          echo "::notice::No GitHub Release found for tag ${GITHUB_REF#refs/tags/}. "
+          echo "The SBOM was generated at ./sbom.spdx.json but was not attached to a release."
+          echo "Ensure the tag was created by the release-please process "
+          "or manually create a release draft."