fix(server): re-export CredentialValidator from crate root

Devolutions#1270 (wildcard cleanup) replaced `pub use server::*` with an explicit
re-export list. This PR predates that change, so without an update the
trait would be defined in server.rs but unreachable from downstream
consumers via `ironrdp_server::CredentialValidator`.

Adds CredentialValidator to the explicit list in lib.rs.

Author: glamberson

crates/ironrdp-server/src/lib.rs

@@ -33,8 +33,8 @@ pub use handler::{KeyboardEvent, MouseEvent, RdpServerInputHandler};
 #[cfg(feature = "helper")]
 pub use helper::TlsIdentityCtx;
 pub use server::{
-    ConnectionHandler, Credentials, PostConnectionAction, RdpServer, RdpServerOptions, RdpServerSecurity, ServerEvent,
-    ServerEventSender,
+    ConnectionHandler, CredentialValidator, Credentials, PostConnectionAction, RdpServer, RdpServerOptions,
+    RdpServerSecurity, ServerEvent, ServerEventSender,
 };
 pub use sound::{RdpsndServerHandler, RdpsndServerMessage, SoundServerFactory};