8643 fix sentry error (#8644)

- fixes missing data in event payload when adding a new workspaceMember
- add strong typing to database event emitters

packages/twenty-server/src/engine/api/graphql/workspace-query-runner/constants/user-signup-event-name.constants.ts

@@ -0,0 +1 @@
+export const USER_SIGNUP_EVENT_NAME = 'user_signup';