Fix: Custom Uri for dotNetRDF (coscine/issues#1912)

src/Blob/Controllers/BlobController.cs

+using Coscine.Api.Blob.Util;
 using Coscine.ApiCommons;
 using Coscine.Configuration;
 using Coscine.Database.DataModel;
@@ -66,7 +67,7 @@ namespace Coscine.Api.Blob.Controllers
         /// <returns> Uri </returns>
         public Uri GenerateId(string resourceId, string path)
         {
-            return new Uri($"https://hdl.handle.net/{_prefix}/{resourceId}@path={Uri.EscapeDataString(path)}");
+            return new CustomUri($"https://hdl.handle.net/{_prefix}/{resourceId}@path={Uri.EscapeDataString(path)}");
         }
 
         /// <summary>
@@ -290,7 +291,7 @@ namespace Coscine.Api.Blob.Controllers
             }
 
             var id = GenerateId(resourceId, path);
-            if (!_rdfStoreConnector.HasGraph(id.AbsoluteUri))
+            if (!_rdfStoreConnector.HasGraph(id))
             {
                 return StatusCode((int)HttpStatusCode.Forbidden,
                     "No metadata set has been added for this file.");