Article store events publisher

[seanwiseman]

Add functionality to publish article events via the walking skeleton's internal event bus.

Should include the publishing of:

• [x] Article version created started/succeeded/failed events
• [x] Article version update started/succeeded/failed events
• [x] Article deleted succeeded/failed events

[thewilkybarkid]

For now we could have:

• article.version.[delete|post|put].started
• article.version.[delete|post|put].completed
• article.version.[delete|post|put].failed

Ties to the API (in name), but this is the processing of the request...

Not sure about the last two though: ok for this purpose, but more generally we might want to consider modelling processes and sub-processes (ie start, step (...), result) in the event bus, rather than just standalone events?

[seanwiseman]

OK sounds good. Yes modelling them would also give a nicer context and would perhaps make it simpler to manage any side effects, such as a failure on step n.