Make rspec random ordering the extension default
Drop deprecation warning for `relation.sum(&:block)`
Use ActiveSupport::JSON as Rabl json_engine

Ensure all data returned by the api is valid json

Fixes #4589
allow product rule to match 'none'

Fixes #4587
Add index to spree_orders for user_id & created_by_id

Addresses potential performance regressions discussed at #4582 in the last_incomplete_spree_order method arising after that method changed in c455e1a

Fixes #4584