update container to expose secrets

Dockerfile

@@ -2,6 +2,10 @@ FROM rocker/shiny-verse:latest
 
 WORKDIR /code
 
+# Expose the secret OPENAI_API_KEY at buildtime and use its value as an environment variable
+RUN --mount=type=secret,id=OPENAI_API_KEY,mode=0444,required=true \
+    echo "OPENAI_API_KEY=$(cat /run/secrets/OPENAI_API_KEY)" > .env
+
 # Install stable packages from CRAN
 RUN install2.r --error \
     shiny \