fix: better validation of events + clean up (#267)

packages/constants/index.ts

@@ -3,6 +3,11 @@ import { differenceInDays, isSameDay, isSameMonth } from 'date-fns';
 export const DEFAULT_ASPECT_RATIO = 0.5625;
 export const NOT_SET_VALUE = '(not set)';
 
+export const RESERVED_EVENT_NAMES = [
+  'session_start',
+  'session_end',
+] as const;
+
 export const timeWindows = {
   '30min': {
     key: '30min',