When creating request:MESSAGE job, new parameter expected

 is recipient_member_ids.

See also:

https://github.com/Libertree/libertree/pull/8
https://github.com/Libertree/libertree-model-rb/pull/5
https://github.com/Libertree/libertree-client-rb/pull/2
https://github.com/Libertree/libertree-backend-rb/pull/5