How to put some classes to same Assembly? Does Microservice architecture make sense in Unity?

Hello guys, I am not very experienced in C#. But I want build my games via component based design (Microservice).
For that I want use Internal methods. What I found out that for it I need to put classes to same assembly.
I tried Stack Overflow but can’t make it work.

Can anyone experienced in C# help me? Or point to some guide? Does it even make sense do it in Unity?

I want have one Service, lets say Scenery Service, this service can have bunch of components but these components will not be accessible from somewhere else then from this Scenery Service, similar design how it is done in Java e.g. Spring boot

I Added screenshot with example.

Thanks

NVM I found answer. Assembly Definitions in Unity - YouTube