This commit fixes an issue where when accepting a contact request
the other end would display an extra notification.
It also changes WaitOnResponse to collect results. This should make
tests less flaky, since sometimes messages are processed in different
batches.
Now we need to be though exact on what we expect from the response (i.e
use == instead of >, otherwise the same behavior applies)
This uncovered a couple of issues with messenger.Merge, so I have moved
the struct to use a map based collection instead of an array.
This commit adds an endpoint to batch the sending of messages.
This is useful to simplify client logic when sending a batch of messages
and ensuring the correct order in the message stream.
It currently implements only what's needed, and naively return an error
if any of the messages fail.