feat: use entrypoint to create user account and copy ssh key

quests/entrypoint.sh

@@ -0,0 +1,16 @@
+#!/bin/sh
+
+USERNAME=commander
+
+if ! id -u ${USERNAME} >/dev/null 2>&1; then
+  adduser --disabled-password --gecos '' --shell /bin/zsh ${USERNAME} && \
+  mkdir -p /home/${USERNAME}/.ssh && \
+  cp /ssh_key.pub /home/${USERNAME}/.ssh/authorized_keys && \
+  chmod 600 /home/${USERNAME}/.ssh/authorized_keys && \
+  chmod 700 /home/${USERNAME}/.ssh && \
+  chown -R ${USERNAME}:${USERNAME} /home/${USERNAME}/.ssh
+fi
+
+mkdir /run/sshd
+echo "Starting SSH server"
+/usr/sbin/sshd -D -e