A 'connection_state Implementations.t
is something that knows how to respond to
many different queries. It is conceptually a package of 'connection_state
Implementation.t
s.
a server that can handle no queries
create ~implementations ~on_unknown_rpc
creates a server capable of responding to
the rpcs implemented in the implementation list. Be careful about setting
on_unknown_rpc
to `Raise
because other programs may mistakenly connect to this
one causing it to crash.