An API to build a UI for queue observability

[samdark]

Proposed new feature or change

We have status($id) now, which is great, but it's not enough to build a UI/command to peek into the current queue state.

See https://github.com/yiisoft/yii2-queue/blob/master/src/cli/InfoAction.php

[samdark]

#272

[samdark]

Likely that's not the job of the primary interface/adapters:

1. Statuses in adapters are largely duplicating what we already know at the app/queue level:

• new and queued when creating a message and pushing it
• in progress, completed, failed in the message handler

2. Adapters such as AMQP don't expose status.
3. Often it matters what is being done by the worker, i.e., how many items of X total are processed, etc., to display progress.