feat: Don't show a contact as verified if their key changed since the verification (#4574)

Don't show a contact as verified if their key changed in the meantime

If a contact's key changed since the verification, then it's very
unlikely that they still have the old, verified key. So, don't show them
as verified anymore.

This also means that you can't add a contact like this to a verified
group, which is good.

The documentation actually already described this (new) behavior:

```rust
/// and if the key has not changed since this verification.
```

so, this adapts the code to the documentation.

src/contact.rs

@@ -1211,7 +1211,6 @@ impl Contact {
     /// and if the key has not changed since this verification.
     ///
     /// The UI may draw a checkbox or something like that beside verified contacts.
-    ///
     pub async fn is_verified(&self, context: &Context) -> Result<VerifiedStatus> {
         // We're always sort of secured-verified as we could verify the key on this device any time with the key
         // on this device
@@ -1220,7 +1219,7 @@ impl Contact {
         }
 
         if let Some(peerstate) = Peerstate::from_addr(context, &self.addr).await? {
-            if peerstate.verified_key.is_some() {
+            if peerstate.is_using_verified_key() {
                 return Ok(VerifiedStatus::BidirectVerified);
             }
         }

src/tests/verified_chats.rs

@@ -627,7 +627,18 @@ async fn test_break_protection_then_verify_again() -> Result<()> {
     e2ee::ensure_secret_key_exists(&bob_new).await?;
 
     tcm.send_recv(&bob_new, &alice, "I have a new device").await;
-    assert_verified(&alice, &bob_new, ProtectionStatus::ProtectionBroken).await;
+
+    let contact = alice.add_or_lookup_contact(&bob_new).await;
+    assert_eq!(
+        contact.is_verified(&alice).await.unwrap(),
+        // Bob sent a message with a new key, so he most likely doesn't have
+        // the old key anymore. This means that Alice's device should show
+        // him as unverified:
+        VerifiedStatus::Unverified
+    );
+    let chat = alice.get_chat(&bob_new).await.unwrap();
+    assert_eq!(chat.is_protected(), false);
+    assert_eq!(chat.is_protection_broken(), true);
 
     {
         let alice_bob_chat = alice.get_chat(&bob_new).await.unwrap();