I was surprised that /join does not return the event ID of my join event

[DMRobertson]

Link to problem area: https://spec.matrix.org/v1.7/client-server-api/#post_matrixclientv3joinroomidoralias

Issue
The room ID is returned. This isn't known the the client at call time, if the client joins via an alias.

I naively expected the event_id to be included in the return payload: ultimately the result of /join is the homeserver making an publishing join event on my behalf. I frequently want to use this when writing E2E tests: join a room, be told what my join event is, then wait for my membership event to appear down /sync.

[turt2live]

matrix-org/matrix-spec-proposals#2943