Migrate from GitLab CI/CD to GitHub actions (#1)

This also adds a new Dockerfile for a e2e-test-image, as the old
image was hosted on our private registry. By having the image located
near the code, we don't have to rely on images on external registries.

deploy/e2e-test-image/Dockerfile

@@ -0,0 +1,9 @@
+# Minimal working Docker image used in our e2e tests
+FROM python:latest
+
+RUN useradd --home-dir /workspace --no-create-home --user-group user && \
+    mkdir /workspace && chown user:user /workspace
+
+WORKDIR /workspace
+
+USER user

deploy/nomad-ci/README.md

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+# Nomad-in-Docker Image
+
+The [`Dockerfile`](Dockerfile) in this folder creates a Docker image that contains Docker and Nomad.
+
+Running the image requires the following Docker options:
+
+- Allow Nomad to use mount: `--cap-add=SYS_ADMIN`
+- Allow Nomad to use bind mounts: `--security-opt apparmor=unconfined`
+- Add access to Docker daemon: `-v /var/run/docker.sock:/var/run/docker.sock`
+- Map port to host: `-p 4646:4646`
+
+A complete command to run the container is as follows.
+
+```shell
+docker run --rm --name nomad \
+  --cap-add=SYS_ADMIN \
+  --security-opt apparmor=unconfined \
+  -v /var/run/docker.sock:/var/run/docker.sock \
+  -p 4646:4646 \
+  nomad-ci
+```