Fix guest user permissions

[Rup-Narayan-Rajbanshi]

Changes

• Add new permission class DenyGuestUserPermission.

Addresses

• https://github.com/IFRCGo/go-api/issues/2255

• [ ] Updated/ran unit tests

• [ ] Updated CHANGELOG.md

[udaynwa]

@szabozoltan69 , when you have time, please review and merge this to Staging.

[szabozoltan69]

@udaynwa – Deployment to Staging is done. No migration was needed.