Fixes https://github.com/matrix-org/matrix-doc/issues/2066
The expectation everywhere is that the `sender` is required. `/initialSync` references StrippedState through a `m.room.member` event reference, and does not need editing.
Fix missed example in make_join
Fix state array in response of send_join
Try removing examples from send_join?
Try printing more information about the error
Copy/paste known working examples
Try schema definitions in the response?