Switch to slim

Dockerfile

@@ -1,4 +1,10 @@
-FROM ruby:3.0.3-bullseye
+FROM ruby:3.0.3-slim-bullseye
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    build-essential \
+    libpq-dev \
+    postgresql-client \
+  && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 WORKDIR /usr/src/app
 
@@ -7,4 +13,3 @@ ENTRYPOINT ["./entrypoint.sh"]
 EXPOSE 3000
 
 CMD ["bundle", "exec", "rails", "s", "-b", "0.0.0.0"]
-