Upgrade API to use django-rest-framework

Currently the Monitoring API uses vanilla Django views to return JSONResponse.

For function based views we should use the @api_view decorator from DRF: https://www.django-rest-framework.org/api-guide/views/#api_view

Once configured, we can use drf-spectacular to automatically provide Swagger documentation.

This would add a lot of value to end users, making the API a lot easier to use and discover.