Implement Default Source Selection Algorithm "By Priority"

[vrann]

Per Source Selection Algorithms HLD

Algorithm steps:

1. Get list of sources sorted by priority (source attribute)
2. Take all available products from 1st source by priority. If some of the products in the order couldn't be delivered from the 1st source - get the rest of products from next by priority source.
3. Repeat Step 2. until all the products from the order would be ready to shipping.

Acceptance Criteria:

1. There is default implementation of the source selection interface via "By Priority" source selection algorithm