I am building a microservice application, and I try to follow the best practices. I use event sourcing and event driven state transfer in many places, but I realized that sometimes I just need to call another service in an asynchronous way to kindly ask it to do something e.g. send out a registration email (as the email service is a technical component and not a domain). I noticed that many times, services just call the other's service API endpoint, but that wouldn't be asynchronous. As I don't expect any returned value when calling from another service, the command would only produce events, RPC is not necessary.
In the end, my plan is to implement commands/actions that can be triggered by clients from REST API (then the commands may also produce responses) or by events or other services from RabbitMQ or similar. This leads me to how should I define the data structure of the command/action, is there any specification for that? Or existing solutions for Python? Or should I do something differently?
