reject invalid role:target early in sender rpc handler

[houqp]

The current behavior is a little bit confusing because it returns 200 to the client, the message won't be delivered later in the code path if role:target is invalid.

[jrgp]

I can't reproduce this. When I try to send to an invalid user using iris.client, I get this:

ValueError: Error response from server, 400: {
    "title": "Request rejected by sender",
    "description": "INVALID role:target"
}

However, I did add tests and more logging to confirm this behavior, and added a few more checks that reject requests that are missing both body and template (which results in not being able to send a message anyway):

#130

[houqp]

Ha, you are right, I missed that extra expand check ;)