Gunicorn is replaced with nginx-unit

We now serve Netbox with an nginx-unit instance instead of Gunicorn.
This allows us to get rid of the extra Nginx container because Unit is
also serving the static files. The static files are now collected at container
buildtime instead of every startup.

docker/launch-netbox.sh

@@ -0,0 +1,53 @@
+#!/bin/bash
+
+UNIT_CONFIG="${UNIT_CONFIG-/etc/unit/nginx-unit.json}"
+UNIT_SOCKET="/opt/unit/unit.sock"
+
+load_configuration() {
+  MAX_WAIT=10
+  WAIT_COUNT=0
+  while [ ! -S $UNIT_SOCKET ]; do
+    if [ $WAIT_COUNT -gte $MAX_WAIT ]; then
+      echo "⚠️ No control socket found; configuration will not be loaded."
+      return 1
+    fi
+
+    WAIT_COUNT=$((WAIT_COUNT + 1))
+    echo "⏳ Waiting for control socket to be created... (${WAIT_COUNT}/${MAX_WAIT})"
+
+    sleep 1
+  done
+
+  # even when the control socket exists, it does not mean unit has finished initialisation
+  # this curl call will get a reply once unit is fully launched
+  curl --silent --output /dev/null --request GET --unix-socket $UNIT_SOCKET http://localhost/
+
+  echo "⚙️ Applying configuration from $UNIT_CONFIG";
+
+  RESP_CODE=$(curl \
+                  --silent \
+                  --output /dev/null \
+                  --write-out '%{http_code}' \
+                  --request PUT \
+                  --data-binary "@${UNIT_CONFIG}" \
+                  --unix-socket $UNIT_SOCKET \
+                  http://localhost/config
+            )
+  if [ "$RESP_CODE" != "200" ]; then
+    echo "⚠️ Could no load Unit configuration"
+    kill "$(cat /opt/unit/unit.pid)"
+    return 1
+  fi
+
+  echo "✅ Unit configuration loaded successfully"
+}
+
+load_configuration &
+
+exec unitd \
+    --no-daemon \
+    --control unix:$UNIT_SOCKET \
+    --pid /opt/unit/unit.pid \
+    --log /dev/stdout \
+    --state /opt/unit/state/ \
+    --tmp /opt/unit/tmp/