…tests

…(ES7)

The use_dis_max parameter was removed from the Elasticsearch query_string
query in ES7. It caused a 400 parsing_exception:
  [query_string] query does not support [use_dis_max]

In ES7 the equivalent behavior is achieved via tie_breaker (default 0.0
gives pure dis_max scoring). Where tie_breaker was already present (product
search) only use_dis_max was removed; where it was absent (admin index search,
help search) removing the flag restores the ES7 default (tie_breaker=0).

Files changed:
- core/app/queries/workarea/search/admin_index_search.rb
- core/app/queries/workarea/search/help_search.rb
- core/app/queries/workarea/search/product_search.rb

…uthorizations

Two interrelated fixes:

1. Pricing::Request#save_order — Mongoid 7 as_document returns nested
   BSON::Document values (e.g. Money fields) that update_attributes!
   cannot properly deserialize. Using as_json performs a deep, recursive
   JSON-safe conversion so Money totals are correctly persisted after
   pricing runs. Also switch reverse_merge to use string key 'items'
   (not symbol) to avoid creating duplicate symbol/string key pairs.

2. Checkout::Steps::Payment#complete? — add credit_card_authorizable?
   guard: if a credit card tender is present its amount must be positive.
   A zero-amount credit card results in a no-op authorization and must
   not allow an order to proceed to placement. This is a defensive check
   on top of the purchasable? amount comparison.

Fixes: payment_test.rb test_complete? refute at line 95
Verified: payment_test, checkout_test, pricing/request_test all green