feat: No implicit member changes from old Delta Chat clients (#7220)

Old Delta Chat clients don't provide timestamps for added and removed members in messages, so at
least implicit member changes may be ignored as it's not clear if they are newer than explicit
member changes from modern clients. Lost messages aren't so frequent anyway, and overall
compatibility with old versions may be limited already.

Author: iequidoo

src/receive_imf.rs

@@ -2864,15 +2864,6 @@ async fn apply_group_changes(
     let (mut removed_id, mut added_id) = (None, None);
     let mut better_msg = None;
     let mut silent = false;
-
-    // True if a Delta Chat client has explicitly added our current primary address.
-    let self_added =
-        if let Some(added_addr) = mime_parser.get_header(HeaderDef::ChatGroupMemberAdded) {
-            addr_cmp(&context.get_primary_self_addr().await?, added_addr)
-        } else {
-            false
-        };
-
     let chat_contacts =
         HashSet::<ContactId>::from_iter(chat::get_chat_contacts(context, chat.id).await?);
     let is_from_in_chat =
@@ -3002,6 +2993,15 @@ async fn apply_group_changes(
             .await?;
         } else {
             let mut new_members: HashSet<ContactId>;
+            // True if a Delta Chat client has explicitly and really added our primary address to an
+            // already existing group.
+            let self_added =
+                if let Some(added_addr) = mime_parser.get_header(HeaderDef::ChatGroupMemberAdded) {
+                    addr_cmp(&context.get_primary_self_addr().await?, added_addr)
+                        && !chat_contacts.contains(&ContactId::SELF)
+                } else {
+                    false
+                };
             if self_added {
                 new_members = HashSet::from_iter(to_ids_flat.iter().copied());
                 new_members.insert(ContactId::SELF);
@@ -3068,10 +3068,9 @@ async fn apply_group_changes(
         .collect();
 
     if let Some(added_id) = added_id {
-        if !added_ids.remove(&added_id) && !self_added {
-            // No-op "Member added" message.
-            //
-            // Trash it.
+        if !added_ids.remove(&added_id) && added_id != ContactId::SELF {
+            // No-op "Member added" message. An exception is self-addition messages because they at
+            // least must be shown when a chat is created on our side.
             better_msg = Some(String::new());
         }
     }