Use constant from TraceAttributes class (#139)

Author: piotrantosik

src/LaravelInstrumentation.php

@@ -42,10 +42,10 @@ public static function register(): void
                 $builder = $instrumentation->tracer()
                     ->spanBuilder(sprintf('HTTP %s', $request?->method() ?? 'unknown'))
                     ->setSpanKind(SpanKind::KIND_SERVER)
-                    ->setAttribute('code.function', $function)
-                    ->setAttribute('code.namespace', $class)
-                    ->setAttribute('code.filepath', $filename)
-                    ->setAttribute('code.lineno', $lineno);
+                    ->setAttribute(TraceAttributes::CODE_FUNCTION, $function)
+                    ->setAttribute(TraceAttributes::CODE_NAMESPACE, $class)
+                    ->setAttribute(TraceAttributes::CODE_FILEPATH, $filename)
+                    ->setAttribute(TraceAttributes::CODE_LINENO, $lineno);
                 $parent = Context::getCurrent();
                 if ($request) {
                     $parent = Globals::propagator()->extract($request, HeadersPropagator::instance());