Added key-based authentication

src/error.rs

@@ -14,6 +14,8 @@ pub enum AppError {
     Child(String),
     #[error("Protocol error: {0}")]
     Protocol(String),
+    #[error("Access denied by server")]
+    AccessDenied,
 }
 
 pub type Result<T> = std::result::Result<T, AppError>;