feat: pre-messages / next version of download on demand (#7371)

Closes <https://github.com/chatmail/core/issues/7367>

Co-authored-by: iequidoo <dgreshilov@gmail.com>
Co-authored-by: Hocuri <hocuri@gmx.de>

src/tests/pre_messages/legacy.rs

@@ -0,0 +1,61 @@
+//! Test that downloading old stub messages still works
+use anyhow::Result;
+
+use crate::download::DownloadState;
+use crate::receive_imf::receive_imf_from_inbox;
+use crate::test_utils::TestContext;
+
+// The code for downloading stub messages stays
+// during the transition perios to pre-messages
+// so people can still download their files shortly after they updated.
+// After there are a few release with pre-message rolled out,
+// we will remove the ability to download stub messages and replace the following test
+// so it checks that it doesn't crash or that the messages are replaced by sth.
+// like "download failed/expired, please ask sender to send it again"
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_download_stub_message() -> Result<()> {
+    let t = TestContext::new_alice().await;
+
+    let header = "Received: (Postfix, from userid 1000); Mon, 4 Dec 2006 14:51:39 +0100 (CET)\n\
+             From: bob@example.com\n\
+             To: alice@example.org\n\
+             Subject: foo\n\
+             Message-ID: <Mr.12345678901@example.com>\n\
+             Chat-Version: 1.0\n\
+             Date: Sun, 22 Mar 2020 22:37:57 +0000\
+             Content-Type: text/plain";
+
+    t.sql
+        .execute(
+            r#"INSERT INTO chats VALUES(
+                    11001,100,'bob@example.com',0,'',2,'',
+                    replace('C=1763151754\nt=foo','\n',char(10)),0,0,0,0,0,1763151754,0,NULL,0,'');
+                "#,
+            (),
+        )
+        .await?;
+    t.sql.execute(r#"INSERT INTO msgs VALUES(
+                11001,'Mr.12345678901@example.com','',0,
+                11001,11001,1,1763151754,10,10,1,0,
+                '[97.66 KiB message]','','',0,1763151754,1763151754,0,X'',
+                '','',1,0,'',0,0,0,'foo',10,replace('Hop: From: userid; Date: Mon, 4 Dec 2006 13:51:39 +0000\n\nDKIM Results: Passed=true','\n',char(10)),1,NULL,0,'');
+        "#, ()).await?;
+    let msg = t.get_last_msg().await;
+    assert_eq!(msg.download_state(), DownloadState::Available);
+    assert_eq!(msg.get_subject(), "foo");
+    assert!(msg.get_text().contains("[97.66 KiB message]"));
+
+    receive_imf_from_inbox(
+        &t,
+        "Mr.12345678901@example.com",
+        format!("{header}\n\n100k text...").as_bytes(),
+        false,
+    )
+    .await?;
+    let msg = t.get_last_msg().await;
+    assert_eq!(msg.download_state(), DownloadState::Done);
+    assert_eq!(msg.get_subject(), "foo");
+    assert_eq!(msg.get_text(), "100k text...");
+
+    Ok(())
+}