Add entrypoint to fix volume permissions at runtime

entrypoint.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+
+# This script ensures that the 'data' directory is owned by the 'appuser'
+# before the main application starts. This is crucial when using Docker volumes,
+# as the mounted directory from the host will be owned by root inside the container.
+
+# Set the ownership of the data directory to the non-root user.
+# The '-R' flag makes it recursive.
+chown -R appuser:appgroup /usr/src/app/data
+
+# Execute the main command (passed as arguments to this script)
+# as the non-root user 'appuser'.
+# 'su-exec' is a lightweight tool to switch users.
+# "$@" passes all arguments from the CMD line.
+exec su-exec appuser "$@"