Strava API Subscription Webhook on Azure Functions

function.json

{
  "bindings": [
    {
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "authLevel": "anonymous",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "res"
    }
  ],
  "disabled": false
}

index.js

const fetch = require('node-fetch');

module.exports = function (context) {
    context.log('Webhook was triggered!');

    if(context.req.method == 'POST') {
      if('owner_id' in context.req.body && 'object_id' in context.req.body) {
        // environment variables: Application settings -> Application settings
        const url = process.env['API_URL'] +
                    '?athlete_id=' + context.req.body.owner_id +
                    '&activity_id=' + context.req.body.object_id;
        // post new activity to your API
        fetch(url)
          .then(function(response) {
            context.log(response.text());
          }).then(function(body) {
            context.res = body.json();
            context.log = body.json();
          })
          .catch(function(error) {
            context.res = {
              status: 502,
              body: error.json() };
            context.log('API returned error: ', error);
          });
      }
    } else {  // [GET]
      if('hub.mode' in context.req.query &&
          context.req.query['hub.verify_token'] == 'STRAVA') {
            context.res = {
              'hub.challenge': context.req.query['hub.challenge'] };
            context.log(
              'hub.challenge received: ', context.req.query['hub.challenge']);
      } else {
        context.res = {
          status: 400,
          body: { error: 'Invalid request: ' + context.req.query.toString() }};
          context.log(
            'Subscribe verification error: ', context.req.query.toString());
      }
    }
    
    context.done();
}

package.json

{
  "name": "<your app>",
  "version": "0.3.1",
  "description": "Provides the Strava Webhook Subscription functionality for the <your app> app.",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Naaman Campbell",
  "license": "MIT",
  "dependencies": {
    "node-fetch": "^1.7.3"
  }
}