Refactor User and Group Creation in Dockerfile for Improved Efficiency and Simplicity

[softjapan]

This pull request refactors the user and group creation process in the Dockerfile to address inefficiencies, reduce redundancy, and enhance simplicity. The following changes have been made:

1. Removed Redundant Existence Checks:

• Eliminated unnecessary getent checks for existing users and groups since the Docker build context typically starts with a clean slate.

2. Unified User and Group Creation into a Single RUN Layer:

• Combined groupadd and useradd commands into a single RUN command to minimize Docker image layers and improve build performance.

3. Added Error Handling:

• Incorporated || true to prevent the build from failing if a group or user already exists, improving robustness in edge cases.

4. Enhanced Readability and Maintainability:

• Simplified and streamlined the commands for better readability and future maintenance.

Before:

ARG GROUP_ID
RUN if ! getent group "$GROUP_ID"; then \
      addgroup --gid "$GROUP_ID" user; \
    fi

ARG USER_ID
RUN if ! getent passwd "$USER_ID"; then \
      adduser --disabled-password --gecos '' --gid "$GROUP_ID" --uid "$USER_ID" user; \
    fi

After:

ARG GROUP_ID
ARG USER_ID

RUN groupadd -g "$GROUP_ID" user || true && \
    useradd -m -u "$USER_ID" -g "$GROUP_ID" -s /bin/bash user || true

Benefits of This Change:
• Improved Efficiency: Fewer layers and streamlined logic result in faster builds and smaller images.
• Reduced Complexity: The refactor removes redundant checks and simplifies user and group creation logic.

Please review and provide feedback!