fix logging

Author: SamSaffron

lib/completions/endpoints/base.rb

@@ -147,6 +147,7 @@ def perform_completion!(
                 end
 
                 response.read_body do |chunk|
+                  response_raw << chunk
                   decode_chunk(chunk).each do |partial|
                     yield partial, cancel
                   end

spec/lib/completions/endpoints/anthropic_spec.rb

@@ -190,6 +190,8 @@
     expect(log.feature_name).to eq("testing")
     expect(log.response_tokens).to eq(15)
     expect(log.request_tokens).to eq(25)
+    expect(log.raw_request_payload).to eq(expected_body.to_json)
+    expect(log.raw_response_payload.strip).to eq(body.strip)
   end
 
   it "supports non streaming tool calls" do