Run tests for Ruby 3.1 and change from racer to mini_racer for Ruby 3.1 support

test-envs/docker-compose-3.1-mysql.yml

@@ -0,0 +1,29 @@
+version: '3'
+services:
+  db:
+    image: mysql:5.7
+    environment:
+      MYSQL_ALLOW_EMPTY_PASSWORD: 1
+      MYSQL_DATABASE: ${TRACKS_DB:-tracks}
+    volumes:
+      - db-data:/var/lib/mysql
+  web:
+    build:
+      context: ..
+      dockerfile: Dockerfile-3.1
+    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: root
+      DATABASE_PASSWORD_EMPTY: 1
+    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: