test: Contact shalln't be verified by another having unknown verifier

It must be verified by "unknown verifier" instead. But if the verifier has known verifier in turn,
it must reverify contacts having unknown verifier. Add a check for this also.

src/receive_imf/receive_imf_tests.rs

@@ -5154,6 +5154,58 @@ async fn test_dont_reverify_by_self_on_outgoing_msg() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_dont_verify_by_verified_by_unknown() -> Result<()> {
+    let mut tcm = TestContextManager::new();
+    let a0 = &tcm.alice().await;
+    let a1 = &tcm.alice().await;
+    let bob = &tcm.bob().await;
+    let fiona = &tcm.fiona().await;
+
+    let bob_chat_id = chat::create_group(bob, "Group").await?;
+    bob.set_chat_protected(bob_chat_id).await;
+    let qr = get_securejoin_qr(bob, Some(bob_chat_id)).await?;
+    tcm.exec_securejoin_qr(a0, bob, &qr).await;
+
+    let qr = get_securejoin_qr(bob, None).await?;
+    tcm.exec_securejoin_qr(fiona, bob, &qr).await;
+
+    // Bob verifies Fiona for Alice#0.
+    let bob_fiona_id = bob.add_or_lookup_contact_id(fiona).await;
+    add_contact_to_chat(bob, bob_chat_id, bob_fiona_id).await?;
+    let sent_msg = bob.pop_sent_msg().await;
+    a0.recv_msg(&sent_msg).await;
+    fiona.recv_msg(&sent_msg).await;
+    let a0_bob = a0.add_or_lookup_contact(bob).await;
+    let a0_fiona = a0.add_or_lookup_contact(fiona).await;
+    assert_eq!(a0_fiona.get_verifier_id(a0).await?, Some(Some(a0_bob.id)));
+
+    let chat_id = a0.create_group_with_members("", &[fiona]).await;
+    a0.set_chat_protected(chat_id).await;
+    a1.recv_msg(&a0.send_text(chat_id, "Hi").await).await;
+    let a1_fiona = a1.add_or_lookup_contact(fiona).await;
+    assert_eq!(a1_fiona.get_verifier_id(a1).await?, Some(None));
+
+    let some_time_to_regossip = Duration::from_secs(20 * 24 * 3600);
+    SystemTime::shift(some_time_to_regossip);
+    let fiona_chat_id = fiona.get_last_msg().await.chat_id;
+    fiona.set_chat_protected(fiona_chat_id).await;
+    a1.recv_msg(&fiona.send_text(fiona_chat_id, "Hi").await)
+        .await;
+    let a1_bob = a1.add_or_lookup_contact(bob).await;
+    // There was a bug that Bob is verified by Fiona on Alice's other device.
+    assert_eq!(a1_bob.get_verifier_id(a1).await?, Some(None));
+
+    SystemTime::shift(some_time_to_regossip);
+    tcm.execute_securejoin(a1, fiona).await;
+    a1.recv_msg(&fiona.send_text(fiona_chat_id, "Hi").await)
+        .await;
+    // But now Bob's verifier id must be updated because Fiona is verified by a known verifier
+    // (moreover, directly), so Alice has reverse verification chains on her devices.
+    assert_eq!(a1_bob.get_verifier_id(a1).await?, Some(Some(a1_fiona.id)));
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn test_sanitize_filename_in_received() -> Result<()> {
     let alice = &TestContext::new_alice().await;