fix: Sort old incoming messages below all outgoing ones (#4621)

If the Inbox is fetched before the Sentbox (as done currently), messages from the Sentbox will
correctly mingle with the Inbox messages in the end. So, this commit changes message ordering only
if we already have processed outgoing messages, e.g. if we just sent them in the chat as described
in #4621. Otherwise new incoming messages are displayed somewhere in the middle of the chat which
doesn't look usable.

src/tests/verified_chats.rs

@@ -480,6 +480,46 @@ async fn test_old_message_4() -> Result<()> {
     Ok(())
 }
 
+/// Alice is offline for some time.
+/// When they come online, first their sentbox is synced and then their inbox.
+/// This test tests that the messages are still in the right order.
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_old_message_5() -> Result<()> {
+    let alice = TestContext::new_alice().await;
+    let msg_sent = receive_imf(
+        &alice,
+        b"From: alice@example.org\n\
+          To: Bob <bob@example.net>\n\
+          Message-ID: <1234-2-4@example.org>\n\
+          Date: Sat, 07 Dec 2019 19:00:27 +0000\n\
+          \n\
+          Happy birthday, Bob!\n",
+        true,
+    )
+    .await?
+    .unwrap();
+
+    let msg_incoming = receive_imf(
+        &alice,
+        b"From: Bob <bob@example.net>\n\
+          To: alice@example.org\n\
+          Message-ID: <1234-2-3@example.org>\n\
+          Date: Sun, 07 Dec 2019 19:00:26 +0000\n\
+          \n\
+          Happy birthday to me, Alice!\n",
+        false,
+    )
+    .await?
+    .unwrap();
+
+    assert!(msg_sent.sort_timestamp == msg_incoming.sort_timestamp);
+    alice
+        .golden_test_chat(msg_sent.chat_id, "test_old_message_5")
+        .await;
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn test_mdn_doesnt_disable_verification() -> Result<()> {
     let mut tcm = TestContextManager::new();