Graceful shutdown and refactor (#144)

* Graceful shutdown and refactor

* ok

* _Graceful_ shutdown

* Remove hardcoded setting

* clean up

* end

* timeout

* hmm

* hmm!

* bash

* bash

* hmm

* maybe maybe

* Adds tests and move non-admin connection rejection to startup (#145)

* Move error response

* Adds tests and removes unused variable

* Adds debug log

Co-authored-by: zainkabani <77307340+zainkabani@users.noreply.github.com>

src/errors.rs

@@ -12,4 +12,5 @@ pub enum Error {
     ClientError,
     TlsError,
     StatementTimeout,
+    ShuttingDown,
 }