don't include the etag header on an entity when using , in line with dataverse (#859)

Author: sean-james-eco

src/Entity.php

@@ -314,7 +314,9 @@ public function get(Transaction $transaction, ?ContextInterface $context = null)
 
         $response = $transaction->getResponse();
         $transaction->assertIfMatchHeader($this->getETag());
-        $transaction->setETagHeader($this->getETag());
+        if (!$transaction->getExpand()->hasValue()) {
+            $transaction->setETagHeader($this->getETag());
+        }
 
         return $response->setResourceCallback($this, function () use ($transaction) {
             $this->emitJson($transaction);

tests/Navigation/Navigation.php

@@ -251,11 +251,12 @@ public function test_create_navigation_property()
 
     public function test_expand_entity()
     {
-        $this->assertJsonResponseSnapshot(
-            (new Request)
-                ->path($this->airportEntitySetPath.'/1')
-                ->expand('flights')
-        );
+        $this
+            ->assertJsonResponseSnapshot(
+                (new Request)
+                    ->path($this->airportEntitySetPath.'/1')
+                    ->expand('flights'))
+            ->assertHeaderMissing('etag');
     }
 
     public function test_expand_hasone_entity()