Add purge to ProducerInterface

[sjparkinson]

Initial draft for resolving #14.

Depends on / based off #15.

Adds the purge method to ProductInterface.

[mathieupinet]

Why the less specific PHPDoc argument?

[sjparkinson]

Personal preference as the type hint is for array, but happy to undo.

[mathieupinet]

ah, I see. I'm sure it's fine then.

[mathieupinet]

looks good otherwise (not tested).

[sjparkinson]

Given the talk today, any thoughts on this @wpillar?

[wpillar]

Here are my thoughts:

• Client implements ProducerInterface and ClientInterface, so adding purge() to ProducerInterface does not unreasonably affect that class.
• You've already got segregated interfaces in ProducerInterface and ClientInterface and since Client implements both, the only consideration really is how people might extend this code. Are we burdening people who might write separate ProducerInterface implementations with a method they can't implement? My thinking here is if we could reasonably assume that all queue implementations have a way of purging then it's fine to put this on ProducerInterface, as a purge operation is similar to a send operation. If we think this assumption is unreasonable then you can segregate further with a PurgeableInterface.

What's your thinking on this?

[sjparkinson]

My thinking here is if we could reasonably assume that all queue implementations have a way of purging then it's fine to put this on ProducerInterface, as a purge operation is similar to a send operation.

So far it's 👌, but I doubt every queue implementation supports purging.

We're not 1.0.0, so I'm going to go with this and see what Mat thinks if he makes use of it.