Clarification needed in invite stripped state

Two areas of the spec doc talk about invite stripped state:

https://matrix.org/docs/spec/client_server/r0.6.1#m-room-member
`invite_room_state` in the Unsigned of your own `m.room.member` event

and

https://matrix.org/docs/spec/client_server/r0.6.1#get-matrix-client-r0-sync
`rooms.invite..invite_state`

The stored event has the `invite_room_state` field but Synapse strips it when including the membership event in `invite_state`. https://github.com/matrix-org/synapse/blob/develop/synapse/rest/client/v2_alpha/sync.py#L326-L341
The `/state` API doesn't work in Synapse pre-join so it seems like a client has no way to ever see a `invite_room_state` in the real world.


js-sdk respects `invite_state` but also expects a `invite_room_state` at the top level (sibling of unsigned) of an event for whatever reason which is obviously wrong.

Compare the two cited Matrix Client-Server specification sections with Synapse's invite handling in synapse/rest/client/v2_alpha/sync.py at lines 326-341. Review the described js-sdk expectations as well. Done means the specification and real-world invite_state behavior are clarified and any inconsistency is explicitly resolved.

Written by the indexing model from the issue text.