Add defer directive to test schemas

Author: calvincestari

Tests/ApolloCodegenTests/CodeGeneration/Templates/SelectionSet/SelectionSetTemplateTests.swift

@@ -1731,7 +1731,7 @@ class SelectionSetTemplateTests: XCTestCase {
         id: String!
         species: String!
       }
-      """
+      """.prefixedWithDeferDirective()
 
     document = """
       query TestOperation {
@@ -1786,7 +1786,7 @@ class SelectionSetTemplateTests: XCTestCase {
         id: String!
         species: String!
       }
-      """
+      """.prefixedWithDeferDirective()
 
     document = """
       query TestOperation {
@@ -5652,7 +5652,7 @@ class SelectionSetTemplateTests: XCTestCase {
         id: String!
         species: String!
       }
-      """
+      """.prefixedWithDeferDirective()
 
     document = """
       query TestOperation {
@@ -8421,3 +8421,13 @@ class SelectionSetTemplateTests: XCTestCase {
   }
 
 }
+
+extension String {
+  fileprivate func prefixedWithDeferDirective() -> String {
+    return """
+    directive @defer(label: String, if: Boolean! = true) on FRAGMENT_SPREAD | INLINE_FRAGMENT
+
+    \(self)
+    """
+  }
+}