[webui][api] Move send_to_bus to RabbitmqBus lib

to make it reusable by other models and to DRY it.

Co-authored-by: Ana María Martínez Gómez <ammartinez@suse.de>
Co-authored-by: Björn Geuken <bgeuken@suse.de>
Co-authored-by: Moisés Déniz <mdeniz@suse.com>
Co-authored-by: David Kang <dkang@suse.com>
Co-authored-by: Eduardo Navarro <enavarro@suse.com>