Implement real messages

[gabrielgiussi]

Goal

Replace A,B,C messages by meaningful messages like 'Create Album, Add Photo, Delete Photo`, like in the examples from this article []
It is way more didactic this way.

Broadcast doesn't write!

However, if I talk about Add Photo it seems like if the process is doing a write and this is not quite accurate, I can explain this or just use it.
Maybe an explanation like "We assume that the system writes the message and then some user could read it but actually the read/write mechanism is implemented by a different abstraction that is not covered in CappIO".