MBIMFetchAttachmentOperation: Add cache headers

kordophone/Bridge/Operations/MBIMFetchAttachmentOperation.m

@@ -124,7 +124,9 @@
             mimeType = [NSString stringWithFormat:@"image/%@", extension];
         }
         
-        response = [[MBIMDataResponse alloc] initWithData:responseData contentType:mimeType];
+        MBIMDataResponse *dataResponse = [[MBIMDataResponse alloc] initWithData:responseData contentType:mimeType];
+        dataResponse.httpHeaders[@"Cache-Control"] = @"public, immutable, max-age=31536000";
+        response = dataResponse;
     } while (0);
     
     self.serverCompletionBlock(response);