fix: set backward verification when observing vc-contact-confirm or…

… `vg-member-added`

Documentation comment says forward and backward verification is set,
but the code was not doing it.
`vc-contact-confirm` and `vg-member-added` messages
indicate that other device finished securejoin protocol
so we know Bob has our key marked as verified.

deltachat-rpc-client/tests/test_securejoin.py

@@ -61,9 +61,16 @@ def test_qr_setup_contact_svg(acfactory) -> None:
 
 
 @pytest.mark.parametrize("protect", [True, False])
-def test_qr_securejoin(acfactory, protect):
+def test_qr_securejoin(acfactory, protect, tmp_path):
     alice, bob = acfactory.get_online_accounts(2)
 
+    # Setup second device for Alice
+    # to test observing securejoin protocol.
+    alice.export_backup(tmp_path)
+    files = list(tmp_path.glob("*.tar"))
+    alice2 = acfactory.get_unconfigured_account()
+    alice2.import_backup(files[0])
+
     logging.info("Alice creates a verified group")
     alice_chat = alice.create_group("Verified group", protect=protect)
     assert alice_chat.get_basic_snapshot().is_protected == protect
@@ -97,6 +104,14 @@ def test_qr_securejoin(acfactory, protect):
     bob_contact_alice_snapshot = bob_contact_alice.get_snapshot()
     assert bob_contact_alice_snapshot.is_verified
 
+    # Start second Alice device.
+    # Alice observes securejoin protocol and verifies Bob on second device.
+    alice2.start_io()
+    alice2.wait_for_securejoin_inviter_success()
+    alice2_contact_bob = alice2.get_contact_by_addr(bob.get_config("addr"))
+    alice2_contact_bob_snapshot = alice2_contact_bob.get_snapshot()
+    assert alice2_contact_bob_snapshot.is_verified
+
 
 def test_qr_securejoin_contact_request(acfactory) -> None:
     """Alice invites Bob to a group when Bob's chat with Alice is in a contact request mode."""

src/securejoin.rs

@@ -637,6 +637,8 @@ pub(crate) async fn observe_securejoin_on_other_device(
         return Ok(HandshakeMessage::Ignore);
     };
     peerstate.set_verified(key.clone(), fingerprint, addr)?;
+    peerstate.backward_verified_key_id =
+        Some(context.get_config_i64(Config::KeyId).await?).filter(|&id| id > 0);
     peerstate.prefer_encrypt = EncryptPreference::Mutual;
     peerstate.save_to_db(&context.sql).await?;