DevRig: PubSub Broadcasts for non-default topics are not received by listeners

[lettucemode]

Brief description
When sending a PubSub Broadcast, if the topic/target is something besides "broadcast" or "global" (for example, "whisper-opaque_user_id"), the broadcast is not received by simulated user views in the Developer Rig.

How to reproduce
Frontend code to listen for broadcasts:

twitch.onAuthorized(function (auth) {
  twitch.listen('whisper-' + auth.userId, function (targ, cType, message) {
   twitch.rig.log(message); // this is never hit
  });
});

Backend code to send a PubSub broadcast (C#):

public async Task SendPubSubWhisper(string channelId, IEnumerable<string> userIds, string message)
{
    using var request = new HttpRequestMessage(HttpMethod.Post,
        $"https://api.twitch.tv/extensions/message/{channelId}");
    request.Headers.Add("Client-ID", this._extClientId);
    request.Headers.Add("Authorization", BEARER_PREFIX + this.MakePubSubToken(channelId, true));

    var body = new Dictionary<string, object>
    {
        { "content_type", "application/json" },
        { "message", message },
        { "targets", userIds.Select(uid => $"whisper-{uid}").ToArray() },
    };
    request.Content = new StringContent(
        new JsonNetSerializer().Serialize(body), Encoding.UTF8, "application/json");

    using var client = new HttpClient();
    using var response = await client.SendAsync(request);
}

private string MakePubSubToken(string channelId, bool isWhisper)
{
    var perms = new perms { send = new string[] { isWhisper ? "whisper-*" : "*" } };
    var payload = new Dictionary<string, object>
    {
        { "exp", (DateTimeOffset.Now.ToUnixTimeSeconds() + 60) },
        { "user_id", this._extOwnerId },
        { "role", "external" },
        { "channel_id", channelId },
        { "pubsub_perms", perms }
    };

    IJwtAlgorithm algorithm = new HMACSHA256Algorithm();
    IJsonSerializer serializer = new JsonNetSerializer();
    IBase64UrlEncoder urlEncoder = new JwtBase64UrlEncoder();
    IJwtEncoder encoder = new JwtEncoder(algorithm, serializer, urlEncoder);
    var token = encoder.Encode(payload, Convert.FromBase64String(this._extSecret));
    return token;
}

Expected behavior
Extensions running in the Developer Rig should receive PubSub broadcast events for any topic/target.

Additional context or questions
The example code above DOES work as expected for all topics/targets when running the extension as a Hosted Test in Twitch. In either case the response from the PubSub Broadcast endpoint is 204 No Content.

[jbulava]

Closing since the Developer Rig has reached its end of support date.