InjectionToken<CngxSidenavContract>
Contract token for a sidenav rail. CngxSidenav provides it via { provide: CNGX_SIDENAV, useExisting: CngxSidenav }, so a collaborator injects the narrow CngxSidenavContract instead of the concrete class.
CngxSidenav
{ provide: CNGX_SIDENAV, useExisting: CngxSidenav }