`mqtt` connecting with longer client id fails

[akrambek]

Describe the bug
mqtt connecting with longer client id fails

To Reproduce
Steps to reproduce the behavior:

1. Start https://github.com/aklivity/zilla-examples/tree/main/mqtt.kafka.broker
2. Run mosquitto_sub -V '5' -t 'newTopic5' -d -i 'Akrams-MacBook-Pro-2_bench_sub_2561494062_1' -q 1 -p 7183
3. See error

Client Akrams-MacBook-Pro-2_bench_sub_2561494062_1 sending CONNECT
Client Akrams-MacBook-Pro-2_bench_sub_2561494062_1 received CONNACK (133)
Connection error: Client Identifier not valid
Client Akrams-MacBook-Pro-2_bench_sub_2561494062_1 sending DISCONNECT

Expected behavior
If you run the same command against mosquito server it works