fix: etag should not be set on any response (#571)

Author: garethgeorge

src/server.ts

@@ -108,7 +108,7 @@ export function getServer(
   app.disable('x-powered-by');
 
   // Disable Express eTag response header
-  app.disable('etag');
+  app.set('etag', false);
 
   if (
     functionSignatureType === 'event' ||

test/integration/http.ts

@@ -105,7 +105,8 @@ describe('HTTP Function', () => {
       )
         .set('Content-Type', 'application/json')
         .expect(test.expectedBody)
-        .expect(test.expectedStatus);
+        .expect(test.expectedStatus)
+        .expect(res => assert(!res.get('etag')));
       assert.strictEqual(callCount, test.expectedCallCount);
     });
   });