Moved cache and messages. Added docs.

src/messages.rs

@@ -0,0 +1,22 @@
+/// These are the nessages that are used by the database.
+use std::sync::mpsc::Sender;
+use uuid::Uuid;
+
+/// Requests of the database.
+pub enum SendMsg {
+    OpenSession(SessionRequest),
+}
+
+/// Responses to database requests
+pub enum ReceiveMsg {
+    Session(Uuid),
+}
+
+
+/// Items needed for a session request.
+pub struct SessionRequest {
+    /// Optional string reprosentation of the session id.
+    pub id: Option<String>,
+    /// Channel Sender for the reply.
+    pub tx: Sender<ReceiveMsg>,
+}