Revert "Make sure that api requires authentication by default"

This reverts commit d24c36b95eb2db5095e09945ecc90f521d7f4f78.
Update inventory after_save

It helps to work some logic with the LineItem because at that point we
would have the record id already. Main motivation here is so that
inventory units wouldn't have a line_item id nil when adding products
via backend to an order (in a product-assembly context)
No need to call gemspec in common_spree_dependencies

Each component Gemfile already calls it
Add index to source columns on spree_adjustments so UpdateAdjustmentStates migration does not take ages to run on large databases

Fixes #4145
Bump activemerchant to 1.42.3
Bump aws-sdk to 1.31.3
Update changelogs
Don't use hard coded assets prefix

Fixes #4156
Remove variant default_scope from Price class this fixes Price must belong to a variant when trying to fetch the price fo a deleted variant

Fixes #4169

Conflicts:
	core/spec/models/spree/variant_spec.rb
Prevents admin js errors by ensuring taxons key in api response

Fixes #4174
Improves Api::ProductsController#create
Fixes duplicate OptionTypes on Api::ProductsController#create
Fixes products_controller_spec
api/products variants spec shouldn't depend on order
Find or create shipping_category on api/products#create

Users can send a shipping_category string on the product payload and
spree will find or create that shipping_category and associate that
category with the product. e.g.

    product: {
      ...
      shipping_category: "Free Shipping Items"
    }
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Append omega to content classes

Fixes #4179
Order#available_payment_methods should also return payment methods marked as 'Both'

Fixes #4199
Add changelog for #4199
Bump acts_as_list to 0.3.0