Add Dockerfile (#19)

*Issue #, if available:* Closes #17

*Description of changes:* Provide a minimal Dockerfile to build a
container for the agent, along with a GitHub action.


By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

Author: simonmarty

.dockerignore

@@ -0,0 +1,4 @@
+.git
+target/
+.github/
+.vscode/

.github/dependabot.yml

@@ -15,3 +15,7 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+  - package-ecosystem: "docker"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/docker.yml

@@ -0,0 +1,24 @@
+name: "Docker Image CI"
+
+on:
+  push:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+      - name: Build
+        uses: docker/build-push-action@v3
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: false
+          tags: test-build:latest

Dockerfile

@@ -0,0 +1,19 @@
+FROM rust:alpine as builder
+
+WORKDIR /app
+
+RUN apk add build-base ca-certificates
+RUN update-ca-certificates
+
+COPY . .
+
+RUN cargo build --release
+
+FROM scratch
+
+WORKDIR /app
+
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /app/target/release/aws_secretsmanager_agent .
+
+ENTRYPOINT [ "./aws_secretsmanager_agent" ]