immediate closing during handshake (RFC 9000 10.2.3)

[Sashan]

I've noticed this while investigating #897 The RFC 9000 10.2.3 comes with this note:

   *  A client will always know whether the server has Handshake keys
      (see Section 17.2.2.1), but it is possible that a server does not
      know whether the client has Handshake keys.  Under these
      circumstances, a server SHOULD send a CONNECTION_CLOSE frame in
      both Handshake and Initial packets to ensure that at least one of
      them is processable by the client.

If I understand things right the scenario goes like this:

• client connects to server
• server accepts connection (call to SSL_accept() returns QSSC (connection object) to server application, keep in mind this may happen before handshake completes
• handshake continues, and eventually server completes handshake and switches from handshake to 1-RTT level
• the packet which confirms server finished handshake sent to client gets lost
• application closes the connection
• in this case server should send CONNECTION_CLOSE notification at handshake as well as on 1-RTT level

[Sashan]

I think this can be delivered after 3.5