Fix solidus stock locations sorting

[ikraamg]

• This might need backporting as this issue has been here for a couple of versions.

Description

There are two challenges that this PR aims to solve:

1. Fixing the sorting of stock locations:

The order of the stock locations that is returned from the configured
sorter is lost in the SimpleCoordinator. This occurs in
the Stock::Availiability class when creating the #stock_item_scope.

Previously, the #sort_availability method
was used to order the stock locations, but this was
lost during the refactor to allow extending the default Solidus
allocation logic.

This re-orders the stock locations for all methods
called by the stock allocators. Namely on_hand_by_stock_location_id
and backorderable_by_stock_location_id

2. Sort stock locations by position after default. (Fix: Sorting Stock Locations #3601)

This is useful because the Admin UI allows the switching of position through a drag and drop interface.
Currently, this interface is not used. It would be more intuitive to have the default stock location used first,
then select the next stock location based on its position column value. For more info, see this issue.

Checklist:

• I have followed Pull Request guidelines
• I have added a detailed description into each commit message
• I have updated Guides and README accordingly to this change (if needed)
• I have added tests to cover this change (if needed)
• I have attached screenshots to this PR for visual changes (if needed)

[ikraamg]

Hey @kennyadsl 👋I thought I would bring the first commit in this PR to your attention, incase you think it's important for the Solidus 3 release.

[ikraamg]

Hey @aldesantis 👋.

I noticed that you had initially worked on the configurable location sorter before it was affected by a refactor.

When you have some time, could you please have a look at this fix?

[aldesantis]

@ikraamg I think this looks good, thank you!

[kennyadsl]

@ikraamg Thanks! Can I ask you a little help with the CHANGELOG entry for this change? I'd like to understand what people upgrading to the next version that contains this change need to know during the upgrade process. As far as I got this change can impact how stocks are allocated during checkout so I want to be sure to provide clear instructions about how to be sure they don't have any negative drawback from this. Thanks!

[ikraamg]

Sure @kennyadsl 👍

The first commit allows for custom stock allocators to work as expected. In other words, before this fix, Solidus technically ignored any custom allocators that stores had configured.

The second commit changes the default solidus stock allocation logic (no custom allocator) by allocating stock first from the warehouse with the default boolean set to true. Thereafter in order of position integer. The position can be changed with the drag and drop interface in the admin panel.

Previously, the default behaviour would have been default first, then in order of name, so the admin drag and drop interface was ignored.

In this image, the stock location named "default" will be used first then the rest by top to bottom: New York, London, Madrid.

@ikraamg Thanks! Can I ask you a little help with the CHANGELOG entry for this change? I'd like to understand what people upgrading to the next version that contains this change need to know during the upgrade process. As far as I got this change can impact how stocks are allocated during checkout so I want to be sure to provide clear instructions about how to be sure they don't have any negative drawback from this. Thanks!