feat!: add field to MlsCommitBundle [WPB-17106]

We need this field to enable advancing the epoch and sharing an
application message with all members immediately when a new epoch is
started.

Author: SimonThormeyer

crypto-ffi/bindings/js/src/CoreCryptoMLS.ts

@@ -73,6 +73,12 @@ export interface CommitBundle {
      * @readonly
      */
     groupInfo: GroupInfoBundle;
+
+    /**
+     * An encrypted message to fan out to all other conversation members in the new epoch
+     * @readonly
+     */
+    encryptedMessage?: Uint8Array;
 }
 
 function commitBundleFromFfi(commitBundle: CommitBundleFfi): CommitBundle {
@@ -84,6 +90,7 @@ function commitBundleFromFfi(commitBundle: CommitBundleFfi): CommitBundle {
             ratchetTreeType: commitBundle.group_info.ratchet_tree_type,
             payload: commitBundle.group_info.payload,
         },
+        encryptedMessage: commitBundle.encryptedMessage,
     };
 }
 

crypto-ffi/src/bundles/commit.rs

@@ -15,18 +15,23 @@ pub struct CommitBundle {
     pub welcome: Option<Vec<u8>>,
     pub commit: Vec<u8>,
     pub group_info: GroupInfoBundle,
+    #[cfg_attr(target_family = "wasm", wasm_bindgen(js_name = "encryptedMessage", readonly))]
+    /// An encrypted message to fan out to all other conversation members in the new epoch
+    pub encrypted_message: Option<Vec<u8>>,
 }
 
 impl TryFrom<MlsCommitBundle> for CommitBundle {
     type Error = CoreCryptoError;
 
     fn try_from(msg: MlsCommitBundle) -> Result<Self, Self::Error> {
+        let encrypted_message = msg.encrypted_message.clone();
         let (welcome, commit, group_info) = msg.to_bytes_triple()?;
         let group_info = group_info.into();
         Ok(Self {
             welcome,
             commit,
             group_info,
+            encrypted_message,
         })
     }
 }

crypto/src/mls/conversation/commit.rs

@@ -41,6 +41,7 @@ impl MlsConversation {
             welcome,
             commit,
             group_info,
+            encrypted_message: None,
         }))
     }
 }
@@ -54,6 +55,8 @@ pub struct MlsCommitBundle {
     pub commit: MlsMessageOut,
     /// `GroupInfo` if the commit is merged
     pub group_info: MlsGroupInfoBundle,
+    /// An encrypted message to fan out to all other conversation members in the new epoch
+    pub encrypted_message: Option<Vec<u8>>,
 }
 
 impl MlsCommitBundle {

crypto/src/mls/conversation/conversation_guard/commit.rs

@@ -138,6 +138,7 @@ impl ConversationGuard {
             commit,
             welcome,
             group_info,
+            encrypted_message: None,
         };
 
         self.send_and_merge_commit(commit).await?;
@@ -187,6 +188,7 @@ impl ConversationGuard {
             commit,
             welcome,
             group_info,
+            encrypted_message: None,
         })
         .await
     }
@@ -263,6 +265,7 @@ impl ConversationGuard {
             welcome,
             commit,
             group_info,
+            encrypted_message: None,
         })
     }
 

crypto/src/transaction_context/conversation/external_commit.rs

@@ -129,6 +129,7 @@ impl TransactionContext {
             welcome: None,
             commit,
             group_info,
+            encrypted_message: None,
         };
 
         let welcome_bundle = WelcomeBundle {