protocol: SignedRefs upgrades provide `SyncedAt`

When upgrading Signed References via `fn upgrad_sigrefs`, the value of
`RepositoryInfo::synced_at` was not updated. Thus, the caller could not
continue with migrated repositories as usual.

Now that enough information about Signed References is propagated, such
as the head of Signed References after upgrade, is available, it is
possible to construct `SyncedAt`.

crates/radicle-protocol/src/service.rs

@@ -447,10 +447,9 @@ where
         let mut private = BTreeSet::new();
 
         for repo in self.storage.repositories()? {
+            let repo = self.upgrade_sigrefs(repo)?;
             let rid = repo.rid;
 
-            self.upgrade_sigrefs(&repo)?;
-
             // If we're not seeding this repo, just skip it.
             if !self.policies.is_seeding(&rid)? {
                 debug!(target: "service", "Local repository {rid} is not seeded");
@@ -522,9 +521,9 @@ where
         Ok(())
     }
 
-    fn upgrade_sigrefs(&mut self, info: &RepositoryInfo) -> Result<(), Error> {
+    fn upgrade_sigrefs(&mut self, mut info: RepositoryInfo) -> Result<RepositoryInfo, Error> {
         if !matches!(info.refs, SignedRefsInfo::NeedsMigration) {
-            return Ok(());
+            return Ok(info);
         }
 
         let rid = info.rid;
@@ -536,8 +535,15 @@ where
 
         let repo = self.storage.repository_mut(rid)?;
         // NOTE: We assume to reach `FeatureLevel::LATEST` by signing refs.
-        repo.force_sign_refs(&self.signer)?;
-        Ok(())
+        let refs = repo.force_sign_refs(&self.signer)?;
+
+        let repo = self.storage.repository(rid)?;
+        let synced_at = SyncedAt::new(refs.at, &repo)?;
+
+        info.synced_at = Some(synced_at);
+        info.refs = SignedRefsInfo::Some(refs);
+
+        Ok(info)
     }
 }