add event base intelligency

models/booking/enums.go

@@ -0,0 +1,23 @@
+package booking
+
+type BookingMode int
+
+const (
+	PLANNED       BookingMode = iota // predictible
+	PREEMPTED                        // can be both predictible or unpredictible, first one asking for a quick exec, second on event, but we pay to preempt in any case.
+	WHEN_POSSIBLE                    // unpredictable, two mode of payment can be available on that case: fixed, or per USE
+)
+
+/*
+Ok make a point there:
+There is 3 notions about booking & payment :
+	Booking mode : WHEN is executed
+	Buying mode : Duration of payment
+	Pricing Mode : How Many time we pay
+
+
+We can simplify Buying Mode and Pricing Mode, some Buying Mode implied limited pricing mode
+Such as Rules. Just like PERMANENT BUYING can be paid only once.
+
+Booking Mode on WHEN POSSIBLE make an exception, because we can't know when executed.
+*/