Prepare to remove "vc-contact-confirm-received", "vg-member-added-received" messages from Securejoin

protocol

src/mimefactory.rs

@@ -917,6 +917,17 @@ impl<'a> MimeFactory<'a> {
                             "Secure-Join".to_string(),
                             "vg-member-added".to_string(),
                         ));
+                        // FIXME: Old clients require Secure-Join-Fingerprint header. Remove this
+                        // eventually.
+                        let fingerprint = Peerstate::from_addr(context, email_to_add)
+                            .await?
+                            .context("No peerstate found in db")?
+                            .public_key_fingerprint
+                            .context("No public key fingerprint in db for the member to add")?;
+                        headers.protected.push(Header::new(
+                            "Secure-Join-Fingerprint".into(),
+                            fingerprint.hex(),
+                        ));
                     }
                 }
                 SystemMessage::GroupNameChanged => {