move session update method to struct implementation

src/client/session/error.rs

@@ -0,0 +1,16 @@
+use std::fmt::{Display, Formatter, Result};
+
+#[derive(Debug)]
+pub enum Error {
+    Connection(crate::client::connection::Error),
+}
+
+impl Display for Error {
+    fn fmt(&self, f: &mut Formatter) -> Result {
+        match self {
+            Self::Connection(e) => {
+                write!(f, "Connection error: {e}")
+            }
+        }
+    }
+}