feat(api): assign and echo request ids

test/api-server_test.ts

@@ -64,6 +64,7 @@ Deno.test('ApiServer serves health metrics and authenticated model listings', as
     assertEquals(healthResponse.status, 200);
     assertEquals(healthBody.status, 'ok');
     assertEquals(healthBody.models, 1);
+    assertEquals(typeof healthResponse.headers.get('x-request-id'), 'string');
 
     const metricsResponse = await fetch(`http://127.0.0.1:${port}/metrics`);
     const metricsBody = await metricsResponse.text();
@@ -79,12 +80,14 @@ Deno.test('ApiServer serves health metrics and authenticated model listings', as
     const authenticatedModels = await fetch(`http://127.0.0.1:${port}/v1/models`, {
       headers: {
         Authorization: 'Bearer valid-key',
+        'X-Request-Id': 'req-test-models',
       },
     });
     const authenticatedBody = await authenticatedModels.json();
     assertEquals(authenticatedModels.status, 200);
     assertEquals(authenticatedBody.object, 'list');
     assertEquals(authenticatedBody.data[0].id, 'meta-llama/Llama-3.1-8B-Instruct');
+    assertEquals(authenticatedModels.headers.get('x-request-id'), 'req-test-models');
 
     const metricsAfterRequests = await fetch(`http://127.0.0.1:${port}/metrics`);
     const metricsAfterRequestsBody = await metricsAfterRequests.text();