TLS Certificate Reloading

[caleblloyd]

Proposed change

#283 introduces a couple callbacks to load TLS Certificates on top of the PEM File paths that already exist

For PEM Files-
On reconnect, reload cert from disk if it has changed.

For Callbacks-
On reconnect, invoke the callback every time.

Document the behavior, so that the end-user knows when to expect that certificate reloading might occur.

Use case

Automatically rotating certificates

Contribution

Yes

[caleblloyd]

#463 changes behavior to construct a new SslClientAuthenticationOptions every time a new connection is made, including loading certs off the filesystem. So certs will technically be reloaded on every reconnect now