Fixed #145 (#150)

* Added "non_relation_field" to types with documentation

* Changed "non_relation_field" to "is_relation"

Whether the nested object is a relation is now an opt-out instead of an opt-in configuration.

* Update SelectFields.php

* Fixed #145, changed  to ->config

Author: roelofjan-elsinga

docs/advanced.md

@@ -919,7 +919,6 @@ class UserType extends GraphQLType
     public function fields()
     {
         return [
-            
             // ...
 
             // JSON column containing all posts made by this user
@@ -935,6 +934,5 @@ class UserType extends GraphQLType
     }
 
     // ...
-
 }
 ```

src/Rebing/GraphQL/Support/SelectFields.php

@@ -139,7 +139,7 @@ protected static function handleFields(array $requestedFields, $parentType, arra
                 $customQuery = array_get($fieldObject->config, 'query');
 
                 // Check if the field is a relation that needs to be requested from the DB
-                $queryable = self::isQueryable($fieldObject);
+                $queryable = self::isQueryable($fieldObject->config);
 
                 // Pagination
                 if(is_a($parentType, PaginationType::class))