Bump @azure/functions from 3.5.1 to 4.2.0 in /backend

Bumps [@azure/functions](https://github.com/Azure/azure-functions-nodejs-library) from 3.5.1 to 4.2.0.
- [Release notes](https://github.com/Azure/azure-functions-nodejs-library/releases)
- [Commits](Azure/azure-functions-nodejs-library@v3.5.1...v4.2.0)

---
updated-dependencies:
- dependency-name: "@azure/functions"
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

backend/package.json

@@ -15,7 +15,7 @@
         "uuid"     : "^9.0.0"
     },
     "devDependencies" : {
-        "@azure/functions" : "^3.2.0",
+        "@azure/functions" : "^4.2.0",
         "@types/node"      : "^18.11.9",
         "@types/uuid"      : "^8.3.4",
         "typescript"       : "^4.8.4"