Refine validations related to SCM webhooks in trigger controller

Skip validation of params only if request comes from and supported SCM

Co-authored-by: Daniel Donisa <daniel.donisa@suse.com>
Co-authored-by: Dany Marcoux <dmarcoux@suse.com>
Co-authored-by: Eduardo Navarro <enavarro@suse.com>
Co-authored-by: Saray Cabrera Padrón <scabrerapadron@suse.de>