exit on heroku-24, add error messaging

Dockerfile

@@ -5,6 +5,7 @@ FROM $BUILD_IMAGE AS builder
 ARG STACK
 
 # Emulate the platform where root access is not available
+USER root
 RUN useradd -d /app non-root-user
 RUN mkdir -p /app /cache /env
 RUN chown non-root-user /app /cache /env
@@ -20,6 +21,7 @@ RUN env -i PATH=$PATH HOME=$HOME STACK=$STACK /buildpack/bin/compile /app /cache
 
 
 FROM $RUNTIME_IMAGE
+USER root
 RUN useradd -d /app non-root-user
 USER non-root-user
 COPY --from=builder --chown=non-root-user /app /app

bin/compile

@@ -13,6 +13,14 @@ unset GIT_DIR
 BUILD_DIR=$1
 BUILDPACK_DIR="$(dirname $(dirname $0))"
 
+STUNNEL=$(command -v stunnel4)
+
+if [ -z $STUNNEL ]; then
+    echo "------> stunnel not detected! stunnel not supported on heroku-24+"
+    echo "------> this buildpack is not required for Redis 6+: https://devcenter.heroku.com/articles/heroku-redis#security-and-compliance"
+    exit 1
+fi
+
 echo "-----> Moving the configuration generation script into app/bin"
 mkdir -p $BUILD_DIR/bin
 cp "$BUILDPACK_DIR/bin/stunnel-conf.sh" $BUILD_DIR/bin/stunnel-conf.sh

bin/start-stunnel

@@ -1,6 +1,14 @@
 #!/usr/bin/env bash
 
 main() {
+  STUNNEL=$(command -v stunnel4)
+
+  if [ -z $STUNNEL ]; then
+      echo "buildpack=stunnel at=error stunnel not detected! stunnel not supported on heroku-24+"
+      echo "buildpack=stunnel at=error this buildpack is not required for Redis 6+: https://devcenter.heroku.com/articles/heroku-redis#security-and-compliance"
+      exit 1
+  fi
+
   if ! is-enabled "${STUNNEL_ENABLED:-1}"; then
     at stunnel-disabled
     exec "$@"