Feature Request - method on Consumer and Producer to check if exchange exists

[JessF298]

It'd be really useful to have a way to check the pre-existance of exchanges (and queues?).

Suggestion: Have a method in each of the consumer and producer classes that checks whether or not an exchange exists using pika function
exchange_declare and passive=True like in the run methods.

Then in the controller, have methods "check_publish_exchange" for out channels in the producer and "check_listening_exchange" for in channels in the consumer.

This makes a user-friendly access point to check if exchanges exist without risking making new ones in production.