Set up basic CI

.drone.yml

@@ -2,9 +2,42 @@ kind: pipeline
 type: docker
 name: default
 
+services:
+  - name: postgres
+    image: docker.io/library/postgres:17.2
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_PASSWORD: postgres
+
 steps:
-- name: greeting
-  image: alpine
-  commands:
-  - echo hello
-  - echo world
+  - name: lint & test
+    image: docker.io/library/elixir:1.18.3-otp-27
+    environment:
+      MIX_ENV: test
+      TEST_POSTGRES_HOST: postgres
+    commands:
+      # Install hex package manager
+      - mix local.hex --force
+      # Fetch dependencies
+      - mix deps.get
+      # Check for compilation errors & warnings
+      - mix compile --warnings-as-errors
+      # Check formatting
+      - mix format --check-formatted
+      # Wait for postgres to become available
+      # TODO: pg_isready is not installed in the elixir image
+      # - |
+      #   for i in {1..20}; do
+      #     pg_isready -h postgres -p $DATABASE_PORT && break
+      #     sleep 2
+      #   done
+      #   echo "Postgres did not become available, aborting"
+      #   exit 1
+      # Security checks
+      - mix sobelow --config
+      # Check dependencies for known vulnerabilities
+      - mix deps.audit
+      # Check for dependencies that are not maintained anymore
+      - mix hex.audit
+      # Run tests
+      - mix test