This API requests that the TLS stack generate a (TLS 1.3)
NewSessionTicket message the next time it is safe to do so (i.e., we do
not have other data pending write, which could be mid-record). For
efficiency, defer actually generating/writing the ticket until there
is other data to write, to avoid producing server-to-client traffic when
not needed.
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11416)
