Include the embedding provider in metrics

It'll probably be useful to know which provider was used.

Author: jackbot

lib/search/results_for_question.rb

@@ -26,6 +26,7 @@ def self.call(question_message)
         embedding_provider: provider,
       )
       metrics[:search_duration] = Clock.monotonic_time - search_start_time
+      metrics[:embedding_provider] = provider
 
       reranking_start_time = Clock.monotonic_time
       weighted_results = Search::ResultsForQuestion::Reranker.call(results)

spec/lib/search/results_for_question_spec.rb

@@ -45,9 +45,9 @@
                             ["not found 2", a_value_between(0.2, 0.3)])
     end
 
-    it "populates the metrics attribute with the durations of the embedding, search, and reranking steps" do
+    it "populates the metrics attribute" do
       result = described_class.call(question_message)
-      expect(result.metrics).to eq({ embedding_duration: 1.5, search_duration: 2.0, reranking_duration: 1.0 })
+      expect(result.metrics).to eq({ embedding_duration: 1.5, search_duration: 2.0, reranking_duration: 1.0, embedding_provider: "openai" })
     end
 
     it "raises an error if the embedding provider is not recognised" do