Add query summary matching

[mkllnk]

This has been copied from the openfoodnetwork repository and adapted slightly. It also needed one little fix.

This approach is quite different to our previous one and I'm wondering if we use User and Create instead of users and insert to stay on the higher level of Active Record. But for now this is can be a simple replacement for the openfoodnetwork spec helper and we can evolve it from there.

The code has been copied from:

https://github.com/openfoodfoundation/openfoodnetwork/blob/a692fc9d125dc2dc62fe8cd536ae5c94df6a4c28/spec/support/query_counter.rb

It has only one usage at the moment:

            query_counter = QueryCounter.new
            get :show, params: { id: order_cycle.id }, as: :json
            expect(query_counter.queries).to eq(
              {
                select: {
                  enterprise_fees: 3,
                  enterprise_groups: 1,
                  enterprises: 22,
                  exchanges: 7,
                  order_cycles: 6,
                  proxy_orders: 1,
                  schedules: 1,
                  spree_roles: 9,
                  spree_variants: 8,
                  tags: 1
                },
                update: { spree_users: 1 }
              }
            )
            query_counter.stop

https://github.com/openfoodfoundation/openfoodnetwork/blob/a692fc9d125dc2dc62fe8cd536ae5c94df6a4c28/spec/controllers/admin/order_cycles_controller_spec.rb#L135-L154

[dacook]

Nice addition!

If there's a way to achieve this using ActiveRecord instead of interpreting SQL, I think that would be much better. But this works :D