feat: extracting environment variables

Dockerfile

@@ -4,13 +4,18 @@ LABEL "repository"="https://github.com/ttionya/vaultwarden-backup" \
   "homepage"="https://github.com/ttionya/vaultwarden-backup" \
   "maintainer"="ttionya <git@ttionya.com>"
 
+ARG USER_NAME="backuptool"
+ARG USER_ID="1100"
+
+ENV LOCALTIME_FILE="/tmp/localtime"
+
 COPY scripts/*.sh /app/
 
 RUN chmod +x /app/*.sh \
-  && apk add --no-cache bash heirloom-mailx p7zip sqlite supercronic tzdata \
-  && ln -sf /tmp/localtime /etc/localtime \
   && mkdir -m 777 /bitwarden \
-  && addgroup -g 1100 backuptool \
-  && adduser -u 1100 -Ds /bin/sh -G backuptool backuptool
+  && apk add --no-cache bash heirloom-mailx p7zip sqlite supercronic tzdata \
+  && ln -sf "${LOCALTIME_FILE}" /etc/localtime \
+  && addgroup -g "${USER_ID}" "${USER_NAME}" \
+  && adduser -u "${USER_ID}" -Ds /bin/sh -G "${USER_NAME}" "${USER_NAME}"
 
 ENTRYPOINT ["/app/entrypoint.sh"]