Add a human-readable message as an attribute representing the event

[alexvanboxel]

Area(s)

area:event

Is your change request related to a problem? Please describe.

Many logging tools have a convention where, upon finding a "message" or "msg" field in a structured log, they'll display its contents prominently for easier user analysis. Since we're establishing event definitions, we can include a human-readable representation of each event. Think of it like a span name in a trace: it carries no inherent meaning but aids user comprehension.

Describe the solution you'd like

Include an event.message attribute that provides a clear, concise, and human-readable description of the event.

Describe alternatives you've considered

Following the convention used in some logging tools, we could try to utilize a message field in the event body. However, this clashes with the principle that each event can freely define its own fields.

Additional context

No response