feat: add user_agent to loggermw (#21485)

Adds the `user_agent` field to `httpmw/loggermw`.

coderd/httpmw/loggermw/logger.go

@@ -80,6 +80,7 @@ func Logger(log slog.Logger) func(next http.Handler) http.Handler {
 			}
 
 			httplog := log.With(
+				slog.F("user_agent", r.Header.Get("User-Agent")),
 				slog.F("host", httpapi.RequestHost(r)),
 				slog.F("path", r.URL.Path),
 				slog.F("proto", r.Proto),

coderd/httpmw/loggermw/logger_internal_test.go

@@ -90,7 +90,7 @@ func TestLoggerMiddleware_SingleRequest(t *testing.T) {
 	}
 
 	// Check that the log contains the expected fields
-	requiredFields := []string{"host", "path", "proto", "remote_addr", "start", "took", "status_code", "latency_ms"}
+	requiredFields := []string{"host", "path", "proto", "remote_addr", "start", "took", "status_code", "user_agent", "latency_ms"}
 	for _, field := range requiredFields {
 		_, exists := fieldsMap[field]
 		require.True(t, exists, "field %q is missing in log fields", field)