Make all catalog product events have same name id. (#10)
* Make all catalog product events have same name id.
This should be useful for stream processing in flink,
because we can then key a stream with these events on the productId
more easily.
* Add product bought event, which is published for each product.
This makes it easier to check whether a product is being oversold.
* Allow for setting the catalog item id through API call.
Previously the entity framework API did have a counter in place,
ignoring the id that was send in the catalog api request.