Function channel

pub fn channel<const SHARDS: usize>(
    initial: CertifiedKey,
) -> (ChannelSender, Arc<ChannelResolver<SHARDS>>)

Create a new resolver channel. The Sender can update the key, and the Receiver can be registered with a rustls server

the SHARDS const generic controlls the size of the channel. A larger channel will reduce contention, leading to faster reads but more writes per call to update.