refactor(imap): move resync request from Context to Imap

For multiple transports we will need to run
multiple IMAP clients in parallel.
UID validity change detected by one IMAP client
should not result in UID resync
for another IMAP client.

src/imap/select_folder.rs

@@ -206,7 +206,7 @@ impl ImapSession {
                             "The server illegally decreased the uid_next of folder {folder:?} from {old_uid_next} to {new_uid_next} without changing validity ({new_uid_validity}), resyncing UIDs...",
                         );
                         set_uid_next(context, folder, new_uid_next).await?;
-                        context.schedule_resync().await?;
+                        self.resync_request_sender.try_send(()).ok();
                     }
 
                     // If UIDNEXT changed, there are new emails.
@@ -243,7 +243,7 @@ impl ImapSession {
             .await?;
 
         if old_uid_validity != 0 || old_uid_next != 0 {
-            context.schedule_resync().await?;
+            self.resync_request_sender.try_send(()).ok();
         }
         info!(
             context,

src/imap/session.rs

@@ -48,6 +48,8 @@ pub(crate) struct Session {
     ///
     /// Should be false if no folder is currently selected.
     pub new_mail: bool,
+
+    pub resync_request_sender: async_channel::Sender<()>,
 }
 
 impl Deref for Session {
@@ -68,6 +70,7 @@ impl Session {
     pub(crate) fn new(
         inner: ImapSession<Box<dyn SessionStream>>,
         capabilities: Capabilities,
+        resync_request_sender: async_channel::Sender<()>,
     ) -> Self {
         Self {
             inner,
@@ -77,6 +80,7 @@ impl Session {
             selected_folder_needs_expunge: false,
             last_full_folder_scan: Mutex::new(None),
             new_mail: false,
+            resync_request_sender,
         }
     }