The goal of the TransparentConfigAcceptor is to support an SNI-based
reverse-proxy, where the server reads the SNI and then transparently
forwards the entire TLS session, ClientHello included, to a backend
server, without terminating the TLS session itself.
This isn't possible with the current LazyConfigAcceptor, which only
allows you to pick a different ServerConfig depending on the SNI, but
will always terminate the session.
The TransparentConfigAcceptor will buffer all bytes read from the
connection (the ClientHello) internally, and then replay them if the
user decides they want to hijack the connection.
The TransparentConfigAcceptor supports all functionality that the
LazyConfigAcceptor does, but due to the internal buffering of the
ClientHello I did not want to add it to the LazyConfigAcceptor, since
it's possible someone wouldn't want to incur that extra cost.