Azure Functions 2.0 extensibility - triggers

This is my second post about Azure Functions extensibility. In the end of previous one I've mentioned that I've been lucky enough to find a real context for my learning adventure. This context came up in chat with colleagues from "friendly" project. They were looking to integrate Azure Functions with RethinkDB. The obvious question is: Why? Cosmos DB is a natural choice for greenfield project which wants to use NoSQL database and serverless approach. Unfortunately not all projects out there are greenfield. There is a lot of brownfield projects, and this "friendly" project of mine fits into this category. They simply can't drop RethinkDB without huge investment (which is planned for later time), so they've decided to use lift and shift approach for migrating existing functionality to Azure. As part of that migration RethinkDB will be containerized and deployed to Azure Container Instances. The desire to be able to use Azure Functions with this setup shouldn't be a surprise, as it adds a lot of value to the migration. The goal is to have below architecture available.