chore: cherry picked various changes from master

Dockerfile

 FROM ruby:2.7.5-slim-bullseye
 
-RUN apt-get update \
-    && DEBIAN_FRONTEND=noninteractive apt-get \
-        -o Dpkg::Options::="--force-confnew" --allow-remove-essential --allow-change-held-packages -fuy \
-        upgrade \
-    && apt-get install -y --no-install-recommends \
-        cmake \
-        pkg-config \
-        default-libmysqlclient-dev \
-        nodejs \
-        curl \
-        git \
-        ruby-dev \
-        telnet \
-        nano \
-        build-essential \
-        libpq-dev \
-        shared-mime-info \
-    && apt-get autoremove \
-    && apt-get autoclean \
-    && apt-get clean \
-    && rm -rf /var/lib/apt/lists/* \
-    && adduser nexus --system --group -u 1000 && mkdir -p /app && chown -R nexus:nexus /app
+# Bootstrap scripts will also be used by stage 2 (rails-runtime-base-image).
+COPY /app/bootstrap*sh /app/
+RUN chmod +x /app/bootstrap*sh
 
-USER nexus
+# Install OS packages required for the gem build environment.
+RUN /app/bootstrap-apt-upgrade.sh && \
+    apt-get install -y --no-install-recommends \
+      build-essential \
+      cmake \
+      curl \
+      default-libmysqlclient-dev \
+      git \
+      libpq-dev \
+      nano \
+      nodejs \
+      pkg-config \
+      ruby-dev \
+      shared-mime-info \
+      telnet && \
+    /app/bootstrap-apt-clean.sh
 
+# Prepare bundle for the gem build environment.
+RUN /app/bootstrap-app-dir.sh
+USER nexus
 WORKDIR /app
 COPY --chown=nexus:nexus Gemfile Gemfile.lock ./
-RUN bundle config --local build.sassc --disable-march-tune-native && gem install bundler -v 2.1 && bundle install --jobs 20 --retry 5
+RUN /app/bootstrap-app-bundle.sh