feat: build the container image with nix

Signed-off-by: Harald Hoyer <harald@matterlabs.dev>

.github/workflows/nix.yml

@@ -0,0 +1,63 @@
+name: nix
+
+on:
+  pull_request:
+    branches: [ "main" ]
+  push:
+    branches: [ "main" ]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
+      - uses: cachix/install-nix-action@6004951b182f8860210c8d6f0d808ec5b1a33d28 # v25
+        with:
+          extra_nix_config: |
+            access-tokens = github.com=${{ github.token }}
+      - run: nix flake check -L --show-trace --keep-going
+
+  fmt:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
+      - uses: cachix/install-nix-action@6004951b182f8860210c8d6f0d808ec5b1a33d28 # v25
+        with:
+          extra_nix_config: |
+            access-tokens = github.com=${{ github.token }}
+      - run: nix fmt
+
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
+      - uses: cachix/install-nix-action@6004951b182f8860210c8d6f0d808ec5b1a33d28 # v25
+        with:
+          extra_nix_config: |
+            access-tokens = github.com=${{ github.token }}
+      - uses: cachix/cachix-action@v14
+        continue-on-error: true
+        with:
+          name: vault-auth-tee
+          authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+          extraPullNames: nixsgx
+      - name: nix build
+        run: nix run nixpkgs#nixci
+      - name: nix docker image
+        run: |
+          nix build .#dockerImage
+          docker load -i result
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USER }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - name: Build and Push Container
+        uses: docker/build-push-action@v5
+        with:
+          tags: matterlabsrobot/vault-auth-tee:latest
+          push: ${{ github.event_name == 'push' ||  github.event_name == 'schedule' }}