implement session update on certificate change in runtime

src/client/session.rs

@@ -0,0 +1,24 @@
+use super::Connection;
+use std::{cell::RefCell, collections::HashMap, rc::Rc};
+
+/// Request sessions holder for `Client` object
+/// * useful to keep connections open and / or validate TLS certificate updates in runtime
+pub struct Session {
+    index: RefCell<HashMap<String, Rc<Connection>>>,
+}
+
+impl Session {
+    pub fn new() -> Self {
+        Self {
+            index: RefCell::new(HashMap::new()),
+        }
+    }
+
+    pub fn get(&self, request: &str) -> Option<Rc<Connection>> {
+        self.index.borrow().get(request).cloned()
+    }
+
+    pub fn update(&self, request: String, connection: Rc<Connection>) -> Option<Rc<Connection>> {
+        self.index.borrow_mut().insert(request, connection)
+    }
+}