fix: Switch to original Hocuri's group membership consistency algo (#3782)(#4624)

- If we don't know the parent (=In-Reply-To) message, then completely recreate the group member list
  (i.e. use the member list of the incoming message) (because we assume that we missed some messages
  & have a wrong group state).
- If the message has a "Chat-Group-Member-Removed: member@example.com" header, then remove this
  member.
- If the message has a "Chat-Group-Member-Added: member@example.com" header, then add this member.

That means:
- Remove checks for the presense of `ContactId::SELF` in the group. Thus all recipients of a message
  take the same decision about group membership changes, no matter if they are in the group
  currently. This fixes a situation when a recipient thinks it's not a member because it missed a
  message about its addition before.
  NOTE: But always recreate membership list if SELF has been added. The older versions of DC don't
  always set "In-Reply-To" to the latest message they sent, but to the latest delivered message (so
  it's a race), so we need this heuristic currently.
- Recreate the group member list if we don't know the parent (=In-Reply-To) message, even if the
  sender isn't in the group as per our view, because we missed some messages and our view may be
  stale.

src/receive_imf/tests.rs

@@ -8,6 +8,7 @@ use crate::chat::{
 };
 use crate::chat::{get_chat_msgs, ChatItem, ChatVisibility};
 use crate::chatlist::Chatlist;
+use crate::config::Config;
 use crate::constants::{DC_GCL_FOR_FORWARDING, DC_GCL_NO_SPECIALS};
 use crate::imap::prefetch_should_download;
 use crate::message::Message;
@@ -3611,3 +3612,62 @@ async fn test_mua_can_readd() -> Result<()> {
     assert!(is_contact_in_chat(&alice, alice_chat.id, ContactId::SELF).await?);
     Ok(())
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_recreate_member_list_on_missing_add_of_self() -> Result<()> {
+    let alice = TestContext::new_alice().await;
+    let bob = TestContext::new_bob().await;
+    let alice_chat_id = create_group_chat(&alice, ProtectionStatus::Unprotected, "Group").await?;
+    add_contact_to_chat(
+        &alice,
+        alice_chat_id,
+        Contact::create(&alice, "bob", &bob.get_config(Config::Addr).await?.unwrap()).await?,
+    )
+    .await?;
+    send_text_msg(&alice, alice_chat_id, "populate".to_string()).await?;
+    alice.pop_sent_msg().await;
+    remove_contact_from_chat(&alice, alice_chat_id, ContactId::SELF).await?;
+    let bob_chat_id = bob.recv_msg(&alice.pop_sent_msg().await).await.chat_id;
+
+    // Bob missed the message adding them, but must recreate the member list.
+    assert_eq!(get_chat_contacts(&bob, bob_chat_id).await?.len(), 1);
+    assert!(is_contact_in_chat(&bob, bob_chat_id, ContactId::SELF).await?);
+    Ok(())
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_recreate_member_list_on_missing_add_of_others() -> Result<()> {
+    let alice = TestContext::new_alice().await;
+    let bob = TestContext::new_bob().await;
+    let alice_chat_id = create_group_chat(&alice, ProtectionStatus::Unprotected, "Group").await?;
+    add_contact_to_chat(
+        &alice,
+        alice_chat_id,
+        Contact::create(&alice, "bob", &bob.get_config(Config::Addr).await?.unwrap()).await?,
+    )
+    .await?;
+    send_text_msg(&alice, alice_chat_id, "populate".to_string()).await?;
+    let bob_chat_id = bob.recv_msg(&alice.pop_sent_msg().await).await.chat_id;
+
+    let fiona = TestContext::new_fiona().await;
+    add_contact_to_chat(
+        &alice,
+        alice_chat_id,
+        Contact::create(
+            &alice,
+            "fiona",
+            &fiona.get_config(Config::Addr).await?.unwrap(),
+        )
+        .await?,
+    )
+    .await?;
+    let fiona_chat_id = fiona.recv_msg(&alice.pop_sent_msg().await).await.chat_id;
+    fiona_chat_id.accept(&fiona).await?;
+
+    send_text_msg(&fiona, fiona_chat_id, "hi".to_string()).await?;
+    bob.recv_msg(&fiona.pop_sent_msg().await).await;
+
+    // Bob missed the message adding fiona, but must recreate the member list.
+    assert_eq!(get_chat_contacts(&bob, bob_chat_id).await?.len(), 3);
+    Ok(())
+}