Added configurable smtp timeout.

- Added config option for smtp timeout
 - Lowered default timeout to 15 seconds instead of default 60.

src/config.rs

@@ -350,6 +350,8 @@ make_config! {
         smtp_password:          Pass,   true,   option;
         /// Json form auth mechanism |> Defaults for ssl is "Plain" and "Login" and nothing for non-ssl connections. Possible values: ["Plain", "Login", "Xoauth2"]
         smtp_auth_mechanism:    String, true,   option;
+        /// SMTP connection timeout |> Number of seconds when to stop trying to connect to the SMTP server
+        smtp_timeout:           u64,     true,   def,     15;
     },
 
     /// Email 2FA Settings