Move to Ruby 2.7 for the default Docker version as well as the default target for alternative DB's. Fix the Ruby image version with three digits because the most recent versions seem to be somehow broken.

test-envs/docker-compose-2.7-postgres.yml

@@ -0,0 +1,32 @@
+version: '3'
+services:
+  db:
+    image: postgres:13
+    environment:
+      POSTGRES_DB: ${DATABASE_NAME:-tracks}
+      POSTGRES_PASSWORD: password
+    volumes:
+      - db-data:/var/lib/postgresql/data
+  web:
+    build:
+      context: ..
+      dockerfile: Dockerfile
+    environment:
+      # These are set in script/ci-build, so we need to pass-thru them.
+      RAILS_ENV: $RAILS_ENV
+      DATABASE_NAME: $DATABASE_NAME
+      DATABASE_USERNAME: postgres
+      DATABASE_PASSWORD: password
+      DATABASE_TYPE: postgresql
+      DATABASE_ENCODING: unicode
+      DATABASE_PORT: 5432
+    volumes:
+      - ${VOLUME:-..}:/app:Z
+      - ${VOLUME:-..}/config/database.docker.yml:/app/config/database.yml:Z
+      - ${VOLUME:-..}/config/site.docker.yml:/app/config/site.yml:Z
+    ports:
+      - 3000:3000
+    depends_on:
+      - db
+volumes:
+  db-data: