How can I setup AMS to create recordings with group write permissions?

[Ben Holness]

### Short description

I want to move and delete recordings with a user that is not antmedia, but has the antmedia group, but when the recordings are saved, they are saved with user only write permissions. How can I change this, so that they save with group write permissions?

### Environment

* Operating system and version: Ubuntu 18

* Ant Media Server version: 2.1 Enterprise Edition

Thanks!