Send EDUs to appservices

[turt2live]

Spec bug: https://github.com/matrix-org/matrix-doc/issues/1145

The use case being bridging read receipts, typing notifications, etc to another network.

[anoadragon453]

Note that some EDUs are now sent after #8437. ToDevice messages are still missing however, which are useful for allowing application services to participant in encrypted rooms (among other things).

[clokep]

Note that some EDUs are now sent after #8437. ToDevice messages are still missing however, which are useful for allowing application services to participant in encrypted rooms (among other things).

@anoadragon453 it looks like #11215 added support for ToDevice messages, does that mean this can now be closed?

[anoadragon453]

Yes, I think so. Consider though that they are still behind several experimental feature flags, and are missing important production-ready features such as retrying failed transactions.

But the feature exists and can be tried out today.