fix: renew IDLE timeout on keepalives and reduce it to 5 minutes

This change depends on async-imap update that resets the timeout
every time an `* OK Still here` is received.

Reducing timeout allows to detect lost connections
not later than 6 minutes
because Delta Chat will attempt to finish IDLE with DONE
after 5 minutes without keepalives
and will either get TCP RST directly
or, worst case, wait another minute for TCP socket read timeout.

Author: link2xt

Cargo.lock

@@ -40,7 +40,7 @@ ratelimit = { path = "./deltachat-ratelimit" }
 
 anyhow = "1"
 async-channel = "2.0.0"
-async-imap = { version = "0.9.1", default-features = false, features = ["runtime-tokio"] }
+async-imap = { version = "0.9.5", default-features = false, features = ["runtime-tokio"] }
 async-native-tls = { version = "0.5", default-features = false, features = ["runtime-tokio"] }
 async-smtp = { version = "0.9", default-features = false, features = ["runtime-tokio"] }
 async_zip = { version = "0.0.12", default-features = false, features = ["deflate", "fs"] }

Cargo.toml

@@ -12,7 +12,13 @@ use crate::context::Context;
 use crate::imap::{client::IMAP_TIMEOUT, FolderMeaning};
 use crate::log::LogExt;
 
-const IDLE_TIMEOUT: Duration = Duration::from_secs(23 * 60);
+/// Timeout after which IDLE is finished
+/// if there are no responses from the server.
+///
+/// If `* OK Still here` keepalives are sent more frequently
+/// than this duration, timeout should never be triggered.
+/// For example, Dovecot sends keepalives every 2 minutes by default.
+const IDLE_TIMEOUT: Duration = Duration::from_secs(5 * 60);
 
 impl Session {
     pub async fn idle(