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/scheduler.rs

@@ -1,7 +1,6 @@
 use std::cmp;
 use std::iter::{self, once};
 use std::num::NonZeroUsize;
-use std::sync::atomic::Ordering;
 
 use anyhow::{Context as _, Error, Result, bail};
 use async_channel::{self as channel, Receiver, Sender};
@@ -481,11 +480,10 @@ async fn inbox_fetch_idle(ctx: &Context, imap: &mut Imap, mut session: Session)
         }
     }
 
-    let resync_requested = ctx.resync_request.swap(false, Ordering::Relaxed);
-    if resync_requested {
+    if let Ok(()) = imap.resync_request_receiver.try_recv() {
         if let Err(err) = session.resync_folders(ctx).await {
             warn!(ctx, "Failed to resync folders: {:#}.", err);
-            ctx.resync_request.store(true, Ordering::Relaxed);
+            imap.resync_request_sender.try_send(()).ok();
         }
     }