Update Rails version in README
Allow users address assignment over API.
Merge pull request #5066 from semenyukdmitriy/readme_rails_414

Update Rails version in README
Add data-hooks to the admin order detail side menu

Fixes #5086
add debugger gems to sandbox

in the same way as in [common_spree_dependencies](https://github.com/spree/spree/blob/adca6cf/common_spree_dependencies.rb#L34-L41)

Closes #5078
Refactor stock related service objects to deal with inventory units.

Prior to this change, stock related service objects (coordinator, packer,
prioritizer, package, adjuster) were tightly coupled to orders and line
items, such that they would only create a set of shipments for the set
of line items for an order.

This change makes those objects work with inventory units, which enables
future enhancements that would create shipments for an order that are
not necessarily tied to the initial purchase (e.g. upcoming exchanges
work).

Fixes #5042
Adds 'current order' API endpoint

This enables an API client to load a user's latest order. At Bonobos, we
use this to load the user's last active cart.

The find_current_order method is broken out to a separate method to
enable gems like spree-multi-store to customize its behavior.