With the help of the bullet gem, and since we remove a couple of N+1s
already, remove them all was just a few keystrokes away. This commits
gets us from 42 SQL queries to 17, and 364.5ms to 253.9ms on my machine
where I just have the sample data's orders. As usual, this will have
a much bigger impact in scenarios with more data.
This removes the N+1 queries caused by
`Api::Admin::OrderSerialier#ready_to_capture` when used from
`Api::OrdersController#index`. While it's fine for the single-order
controller actions, it's not for this one that deals with a collection
of orders.
Fortunately, `SearchOrders` is used only in this controller action so we
can put the `includes` calls there, otherwise, we would need to refactor
it a bit to pass in a context-specific AR relation.
The q['inventory_items_shipment_id_null'] search element was generating duplicates where there were multiple line items on an order that were ready to be shipped, with id = null
