Set a reliable UID and GID for olivetin user.

Dockerfile

@@ -1,6 +1,6 @@
 FROM fedora
 
-RUN useradd -rm olivetin
+RUN useradd -rm olivetin -u 1000 -g 1000
 
 RUN mkdir -p /config /var/www/olivetin/ && \
     dnf install -y \