Update Dockerfile

Dockerfile

@@ -6,8 +6,9 @@ ENV POSTGRES_DB=mydb
 ENV POSTGRES_USER=myuser
 ENV POSTGRES_PASSWORD=mypassword
 
-# Create a custom user and group for PostgreSQL
-RUN groupadd -r postgres && useradd -r -g postgres postgres
+# Check if the postgres user and group exist, and create them if not
+RUN if ! id -g postgres > /dev/null 2>&1; then groupadd -r postgres; fi
+RUN if ! id -u postgres > /dev/null 2>&1; then useradd -r -g postgres postgres; fi
 
 # Set the ownership of the data directory
 RUN mkdir -p /var/lib/postgresql/data && chown -R postgres:postgres /var/lib/postgresql/data