admit
Decide whether a handshaked link may join.
Return
true to admit the link; false to close the connection and reject it with LinkRejectedException.
Parameters
principal
the host-verified identity riding the connection (attached by the transport accept via withPrincipal); null = unattested.
remoteId
the peer id the joiner claimed in its MeshHello preamble (self-asserted, unverified).