docs: ADR for adding event bus kafka cookiecutter

Author: jesperhodge

docs/decisions/0007-event-bus-kafka-cookiecutter.rst

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+7. Adding Cookiecutter for new Event Bus events and their kafka setup
+#####################################################################
+
+Status
+******
+
+Proposed
+
+
+Context
+*******
+
+Adding new events to the Openedx Event Bus has taken a lot of time and effort in the past.
+Specifically, setting up local development with Kafka and connecting it correctly to the new provider,
+consumer, and topic has been a challenge.
+We want to make this process easier by creating a Cookiecutter template that can be used to
+quickly scaffold the necessary files and configurations for a new Event Bus event.
+
+This approach involves not creating one new project directory, but instead code that can be copied
+into multiple existing repositories.
+
+
+Decision
+********
+
+* We will add a new folder `cookiecutter/new-event-bus-kafka-event` to the edx-cookiecutters repository.
+
+* This folder will contain subfolders for each of the following:
+  - `openedx-events`: Contains the Open edX event definitions to be copied to the `openedx-events` repository.
+  - `provider`: Contains the code for the new provider, as well as any necessary configuration files and environment
+    variables needed to connect to the Kafka Event Bus, to be copied to the repository the new provider will be created in.
+  - `consumer`: Contains the code for the new consumer, as well as any necessary configuration files and environment
+    variables needed to connect to the Kafka Event Bus, to be copied to the repository the new consumer will be created in.
+    Also includes a docker-compose file to run the consumer locally.
+
+* Where needed, in the future we should add similar cookiecutter templates for the other Event Bus implementations,
+  such as redis, rather than making duplicate work necessary every time a new event is added.
+
+* We will add well-visible central documentation to Confluence to make it easy to find and use this cookiecutter template.
+
+
+Rejected Alternatives
+*********************
+
+Keep template private
+=====================================================
+
+* Since the Kafka implementation of the EventBus is part of Openedx, we should also
+  make the cookiecutter template available to the Open edX community.
+
+Supporting other Event Bus implementations
+=====================================================
+
+Creating templates for multiple Event Bus implementations, including redis, is desirable in the future,
+but the immediate need is for the Kafka implementation. Doing the same for redis will need a new large effort.
+Currently, the config needed for Kafka has been surfaced by 2U discovery (Quokkas team), providing the knowledge
+needed to create the Kafka implementation template.