Expose various test brokers

[fmvilas]

Use our Digital Ocean credits to host various message brokers for people to use during testing/development. They would wipe out all the data daily or even every few hours to make sure it doesn't grow too much.

List of brokers/protocols to expose:

• Kafka
• AMQP 0-9-1 (RabbitMQ)
• AMQP 1.0 (ActiveMQ)
• MQTT (Mosquitto)
• MQTT over WebSocket (Mosquitto)
• WebSocket (an echo server)
• Socket.IO (an echo server)

These could potentially be used from Studio and CLI. Even the website docs and the generated docs can make use of them.