Improve docker setup

Dockerfile

@@ -1,8 +1,5 @@
-FROM ruby:2.4.0
-ENV APP_HOME /app/
-ENV LIB_DIR lib/front_matter_parser/
-RUN mkdir -p $APP_HOME/$LIB_DIR
-WORKDIR $APP_HOME
-COPY Gemfile *gemspec $APP_HOME
-COPY $LIB_DIR/version.rb $APP_HOME/$LIB_DIR
-RUN bundle install
+FROM ruby:3.0.0
+ENV APP_USER front_matter_parser_user
+RUN useradd -ms /bin/bash $APP_USER
+USER $APP_USER
+WORKDIR /home/$APP_USER/app

docker-compose.yml

@@ -2,6 +2,11 @@ version: '2'
 services:
   app:
     build: .
-    command: tail -f Gemfile
+    image: front_matter_parser_user
+    command: bash -c "bundle && tail -f Gemfile"
     volumes:
-      - .:/app
+      - .:/home/front_matter_parser_user/app
+    tty: true
+    stdin_open: true
+    tmpfs:
+      - /tmp