Add http.version to client/server traces.

.github/workflows/test.yaml

@@ -7,6 +7,8 @@ permissions:
 
 env:
   CONSOLE_OUTPUT: XTerm
+  TRACES_BACKEND: traces/backend/test
+  METRICS_BACKEND: metrics/backend/test
 
 jobs:
   test:

lib/async/http/client.rb

@@ -165,6 +165,10 @@ def call(request)
 						end
 
 						super.tap do |response|
+							if version = response&.version
+								span['http.version'] = version
+							end
+
 							if status = response&.status
 								span['http.status_code'] = status
 							end

lib/async/http/server.rb

@@ -81,6 +81,7 @@ def call(request)
 					end
 
 					attributes = {
+						'http.version': request.version,
 						'http.method': request.method,
 						'http.authority': request.authority,
 						'http.scheme': request.scheme,