limit access to thumbnails

Signed-off-by: tobiasKaminsky <tobias@kaminsky.me>

src/main/AndroidManifest.xml

@@ -256,6 +256,8 @@
         <provider
             android:name=".providers.DiskLruImageCacheFileProvider"
             android:authorities="@string/image_cache_provider_authority"
+            android:grantUriPermissions="true"
+            android:readPermission="android.permission.MANAGE_DOCUMENTS"
             android:exported="true">
         </provider>
 

src/main/java/com/owncloud/android/ui/helpers/FileOperationsHelper.java

@@ -751,6 +751,7 @@ public class FileOperationsHelper {
                     context.getResources().getString(R.string.image_cache_provider_authority) +
                     file.getRemotePath()));
             sendIntent.putExtra(Intent.ACTION_SEND, true);      // Send Action
+            sendIntent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
 
             mFileActivity.startActivity(Intent.createChooser(sendIntent,
                     context.getString(R.string.actionbar_send_file)));