Implement sending ephemeral events to appservices (MSC2409)

[matrixbot]

This issue was originally created by @bodqhrohro at matrix-org/dendrite#1566.

Description:

Dunno what's that for (probably some custom extension), but matrix-appservice-node generates configs with that key, and Dendrite fails to read it, so I had to remove the following line manually. Ideally, the config parser should just ignore unknown keys.

[matrixbot]

This comment was originally posted by @tulir at matrix-org/dendrite#1566 (comment).

This should probably be split into two issues:

1. Ignore unknown keys in appservice registration files
2. Implement sending ephemeral events to appservices (MSC2409)

[matrixbot]

This comment was originally posted by @bodqhrohro at matrix-org/dendrite#1566 (comment).

Done, I've split the parsing issue out: #1567

[matrixbot]

This comment was originally posted by @Kab1r at matrix-org/dendrite#1566 (comment).

It's been a while and ignoring unknown keys is solved, so I might take a look at implementing this

[matrixbot]

This comment was originally posted by @Blintmester at matrix-org/dendrite#1566 (comment).

Is there any progress on this? I am excited to see when it will be ready!

[matrixbot]

This comment was originally posted by @apprehensions at matrix-org/dendrite#1566 (comment).

Anything new?