Use v2 for all site search queries

This switches the `/search/all` ("site search") finder over to use
`search-api-v2` exclusively now that our AB test has concluded with a
positive outcome.

- Instead of checking for AB test variant, check for site search finder
  base path to establish whether to use v2
- Add `use_v1` query parameter along the lines of the existing `use_v2`
  to force use of `search-api` in circumstances where `search-api-v2`
  would normally be used

app/lib/search/query.rb

@@ -2,6 +2,8 @@
 # search results from rummager.
 module Search
   class Query
+    SITE_SEARCH_FINDER_BASE_PATH = "/search/all".freeze
+
     include ActiveModel::Validations
 
     attr_reader :filter_params
@@ -110,7 +112,10 @@ def fetch_search_response(content_item)
     end
 
     def use_v2_api?
-      ActiveModel::Type::Boolean.new.cast(filter_params["use_v2"]) || ab_params[:vertex] == "B"
+      return false if ActiveModel::Type::Boolean.new.cast(filter_params["use_v1"])
+      return true if ActiveModel::Type::Boolean.new.cast(filter_params["use_v2"])
+
+      content_item.base_path == SITE_SEARCH_FINDER_BASE_PATH
     end
   end
 end

spec/controllers/finders_controller_spec.rb

@@ -425,7 +425,7 @@
 
   describe "with legacy query parameters for publications" do
     before do
-      search_api_request
+      search_api_request(search_api_app: "search-api-v2")
       stub_content_store_has_item("/search/all", all_content_finder)
 
       @default_params = { slug: "search/all" }

spec/lib/search/query_spec.rb

@@ -18,6 +18,7 @@ def stub_batch_search
       "details" => {
         "facets" => facets,
       },
+      "base_path" => "/some/finder",
     )
   end
 
@@ -49,6 +50,26 @@ def result_item(id, title, score:, popularity:, updated:)
     }
   end
 
+  context "when manually overriding parameters to use the v1 API" do
+    subject { described_class.new(content_item, { "use_v1" => "true" }).search_results }
+
+    let(:content_item) { ContentItem.new({ "base_path" => "/search/all" }) }
+
+    before do
+      stub_search.to_return(body: {
+        "results" => [
+          result_item("/i-am-the-v1-api", "I am the v1 API", score: nil, updated: "14-12-19", popularity: 1),
+        ],
+      }.to_json)
+    end
+
+    it "calls the v1 API" do
+      results = subject.fetch("results")
+      expect(results.length).to eq(1)
+      expect(results.first).to match(hash_including("_id" => "/i-am-the-v1-api"))
+    end
+  end
+
   context "when manually overriding parameters to use the v2 API" do
     subject { described_class.new(content_item, { "use_v2" => "true" }).search_results }
 
@@ -67,8 +88,10 @@ def result_item(id, title, score:, popularity:, updated:)
     end
   end
 
-  context "when in AB test variant B" do
-    subject { described_class.new(content_item, {}, ab_params: { vertex: "B" }).search_results }
+  context "when on the site search finder" do
+    subject { described_class.new(content_item, {}).search_results }
+
+    let(:content_item) { ContentItem.new({ "base_path" => "/search/all" }) }
 
     before do
       stub_search_v2.to_return(body: {