Function build_router 

pub fn build_router<UD, SL, SR, IR>(
    underlay_discovery: UD,
    snap_cp_api: Url,
    segment_lister: SL,
    snap_resolver: SR,
    identity_registry: Arc<IR>,
    pg_wap_session_manager: Option<Arc<dyn PgWapSessionManager>>,
    token_verifier: SnapTokenVerifier,
    metrics: Metrics,
) -> Result<Router>
where
    UD: UnderlayDiscovery + 'static + Send + Sync,
    SL: SegmentsDiscovery + 'static + Send + Sync,
    SR: SnapDataPlaneResolver + 'static + Send + Sync,
    IR: SnapTunIdentityRegistry + 'static + Send + Sync,

Builds the SNAP control plane router.