S2S v1 send_join: `event` response property not documented

[joepie91]

Link to problem area: https://spec.matrix.org/v1.6/server-server-api/#put_matrixfederationv1send_joinroomideventid

Issue

Aside from auth_chain, origin, and state, the example response also shows an event property, but it is not specified what this is (although it seems to be the signed event generated by the resident homeserver).

As this is top-level in the response and not part of an event, it's not already covered by the various "event format may change" warnings, and indeed this does not seem to be specified in the room version spec either.

[richvdh]

I think the example is wrong here - it seems to have been added since v1.1, but send_join v1 shouldn't have changed.

[richvdh]

(would be good to do some git archaeology to figure out when/why this changed)

[DMRobertson]

(would be good to do some git archaeology to figure out when/why this changed)

6c4aabd#diff-939da761da20aa08a64a2e403cad5d6d4accbc749ca76d63d67e7b29f7fff0daR344

The title of which refers to matrix-org/matrix-spec-proposals#3387, see https://github.com/matrix-org/matrix-spec-proposals/pull/3387/files#diff-939da761da20aa08a64a2e403cad5d6d4accbc749ca76d63d67e7b29f7fff0daR344

It looks like this commit introduced this: matrix-org/matrix-spec-proposals@2ccae80#diff-939da761da20aa08a64a2e403cad5d6d4accbc749ca76d63d67e7b29f7fff0daR337

maybe in response to this comment? https://github.com/matrix-org/matrix-spec-proposals/pull/3387/files#r704355365

I can't see any v2-but-not-v1 discussion around this.