Added lookup of location by URL Alias

```
location(urlAlias: "/") {}
```

src/GraphQL/DataLoader/LocationLoader.php

@@ -42,6 +42,13 @@ public function findById($id): Location;
      */
     public function findByRemoteId($remoteId): Location;
 
+    /**
+     * @param string $remoteId A location remote id
+     *
+     * @return \eZ\Publish\API\Repository\Values\Content\Location
+     */
+    public function findByUrlAlias(string $urlAlias): Location;
+
     /**
      * Counts the results of a query.
      *

src/GraphQL/DataLoader/SearchLocationLoader.php

@@ -7,7 +7,9 @@
 namespace EzSystems\EzPlatformGraphQL\GraphQL\DataLoader;
 
 use eZ\Publish\API\Repository\LocationService;
+use eZ\Publish\API\Repository\URLAliasService;
 use eZ\Publish\API\Repository\Values\Content\LocationQuery;
+use eZ\Publish\API\Repository\Values\Content\URLAlias;
 use EzSystems\EzPlatformGraphQL\GraphQL\DataLoader\Exception\ArgumentsException;
 use eZ\Publish\API\Repository\Exceptions as ApiException;
 use eZ\Publish\API\Repository\SearchService;
@@ -30,10 +32,16 @@ class SearchLocationLoader implements LocationLoader
      */
     private $locationService;
 
-    public function __construct(SearchService $searchService, LocationService $locationService)
+    /**
+     * @var \eZ\Publish\API\Repository\URLAliasService
+     */
+    private $urlAliasService;
+
+    public function __construct(SearchService $searchService, LocationService $locationService, URLAliasService $urlAliasService)
     {
         $this->searchService = $searchService;
         $this->locationService = $locationService;
+        $this->urlAliasService = $urlAliasService;
     }
 
     public function find(LocationQuery $query): array
@@ -66,6 +74,15 @@ public function findByRemoteId($id): Location
         }
     }
 
+    public function findByUrlAlias(string $urlAlias): Location
+    {
+        $alias = $this->urlAliasService->lookup($urlAlias);
+
+        return ($alias->type == URLAlias::LOCATION)
+            ? $this->locationService->loadLocation($alias->destination)
+            : null;
+    }
+
     /**
      * Counts the results of a query.
      *

src/GraphQL/Resolver/LocationResolver.php

@@ -64,6 +64,8 @@ public function resolveLocation($args)
             return $this->locationLoader->findById($args['locationId']);
         } elseif (isset($args['remoteId'])) {
             return $this->locationLoader->findByRemoteId($args['remoteId']);
+        } elseif (isset($args['urlAlias'])) {
+            return $this->locationLoader->findByUrlAlias($args['urlAlias']);
         }
 
         throw new ArgumentsException('Requires one and only one of remoteId or locationId');

src/Resources/config/graphql/Repository.types.yml

@@ -12,6 +12,9 @@ Repository:
                     remoteId:
                         description: "A location remote id"
                         type: "Int"
+                    urlAlias:
+                        description: "A location url alias: 'path/to/content-item'"
+                        type: "String"
                 resolve: "@=resolver('Location', [args])"
             contentType:
                 type: "ContentType"