[FS-919] Support Basic Processing of External Commits (#2765)

* Check external commit criteria
- Extract the key package from the update path
- Validate key package before replacing the old one
* Fix the serialiseMLS instance for `Sender 'MLSPlainText`
* Update the mls-test-cli reference
* Integration tests for external commits

Author: mdimjasevic

services/galley/test/integration/API/MLS.hs

@@ -1050,6 +1050,64 @@ testExternalCommitNewClient = do
 
 -- the list of members should be [alice1, bob1]
 
+testExternalCommitNotMember :: TestM ()
+testExternalCommitNotMember = do
+  [alice, bob] <- createAndConnectUsers (replicate 2 Nothing)
+
+  runMLSTest $ do
+    [alice1, alice2, bob1] <- traverse createMLSClient [alice, alice, bob]
+    traverse_ uploadNewKeyPackage [bob1, alice2]
+    (_, qcnv) <- setupMLSGroup alice1
+
+    -- so that we have the public group state
+    void $ createAddCommit alice1 [alice] >>= sendAndConsumeCommitBundle
+
+    pgs <-
+      LBS.toStrict . fromJust . responseBody
+        <$> getGroupInfo (ciUser alice1) qcnv
+    mp <- createExternalCommit bob1 (Just pgs) qcnv
+    bundle <- createBundle mp
+    postCommitBundle (ciUser (mpSender mp)) bundle
+      !!! const 404 === statusCode
+
+testExternalCommitSameClient :: TestM ()
+testExternalCommitSameClient = do
+  [alice, bob] <- createAndConnectUsers (replicate 2 Nothing)
+
+  runMLSTest $ do
+    [alice1, bob1] <- traverse createMLSClient [alice, bob]
+    void $ uploadNewKeyPackage bob1
+    (_, qcnv) <- setupMLSGroup alice1
+    void $ createAddCommit alice1 [bob] >>= sendAndConsumeCommitBundle
+
+    let rejoiner = alice1
+    ecEvents <- createExternalCommit rejoiner Nothing qcnv >>= sendAndConsumeCommitBundle
+    liftIO $
+      assertBool "No events after external commit expected" (null ecEvents)
+
+    message <- createApplicationMessage bob1 "hello"
+    void $ sendAndConsumeMessage message
+
+testExternalCommitNewClient :: TestM ()
+testExternalCommitNewClient = do
+  [alice, bob] <- createAndConnectUsers (replicate 2 Nothing)
+
+  runMLSTest $ do
+    [alice1, bob1] <- traverse createMLSClient [alice, bob]
+    void $ uploadNewKeyPackage bob1
+    (_, qcnv) <- setupMLSGroup alice1
+    void $ createAddCommit alice1 [bob] >>= sendAndConsumeCommitBundle
+
+    nc <- createMLSClient bob
+    ecEvents <- createExternalCommit nc Nothing qcnv >>= sendAndConsumeCommitBundle
+    liftIO $
+      assertBool "No events after external commit expected" (null ecEvents)
+
+    message <- createApplicationMessage nc "hello"
+    void $ sendAndConsumeMessage message
+
+-- the list of members should be [alice1, bob1]
+
 testAppMessage :: TestM ()
 testAppMessage = do
   users@(alice : _) <- createAndConnectUsers (replicate 4 Nothing)