Add script to add delta handler

This script at least ensures it looks the same in various services.  A more
streamlined solution may be preferred in the future.

Author: madnificent

README.md

@@ -148,11 +148,18 @@ docker-compose up -d your-microservice-name
 You can install additional dependencies by including a `package.json` file next to your `app.js`. It works as you would expect: just define the packages in the `dependencies` section of the `package.json`. They will be installed automatically at build time and in development mode. There is no need to restart the container.
 
 ### Handle delta's from the delta-service
-If you are building a reactive service that should execute certain logic based on changes in the database, you want to hook it up to the [delta-notifier](https://github.com/mu-semtech/delta-notifier/). Some extra steps need to be taken to properly handle delta's, specifically the route handling delta's will need to use a specific bodyParser. 
+If you are building a reactive service that should execute certain logic based on changes in the database, you want to hook it up to the [delta-notifier](https://github.com/mu-semtech/delta-notifier/). Some extra steps need to be taken to properly handle delta's, specifically the route handling delta's will need to use a specific bodyParser.
 
 The default bodyParser provided by the template will only accept `application/vnd.api+json` and the delta-notifier is sending `application/json` content. Aside from that the body of a delta message may be very large, often several megabytes. By specifying the bodyParser on the route accepting delta messages you can easily modify it when required.
 
-An example
+The mu script `add-delta-handler` can be ran to update your app.js file:
+
+```bash
+mu script add-delta-handler
+```
+
+The resulting changes will look similar to:
+
 ```javascript
 // app.js
 import bodyParser from 'body-parser';

scripts/add-delta-handler/run.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+if [ -f /app/app.js ]
+then
+    APP_COPY=$(mktemp)
+    cp /app/app.js "$APP_COPY"
+    awk '!/^import/ && !x {print "import bodyParser from \"body-parser\";"; x=1} 1' "$APP_COPY" >/app/app.js
+    rm "$APP_COPY"
+
+    cat <<EOF>> /app/app.js
+
+app.post('/delta', bodyParser.json({ limit: '50mb' }), (req, _res) => {
+  for( const {inserts, deletes: _deletes} of req.body ) {
+    for( const triple of inserts ) {
+      console.log(triple.subject.value, triple.predicate.value, triple.object.value);
+    }
+  }
+});
+EOF
+else
+    echo "Can only insert into app.js"
+fi

scripts/config.json

@@ -28,6 +28,21 @@
       "mounts": {
         "service": "/app"
       }
+    },
+    {
+      "documentation": {
+        "command": "add-delta-handler",
+        "description": "Sets up the delta handler for the scripts",
+        "arguments": []
+      },
+      "environment": {
+        "image": "ubuntu:25.10",
+        "interactive": false,
+        "script": "add-delta-handler/run.sh"
+      },
+      "mounts": {
+        "service": "/app"
+      }
     }
   ]
 }