feat(core,app,android,ios): rename a share

ShareStore::rename changes only the name; the id that the catalog, watch
state and offline files are keyed by stays the same. Sync carries the
change as it does any other change to the share's register. The desktop
renames in the share's row. The phones rename from the share's menu.
Before, the name given at add time was permanent short of removing the
share.

crates/pstr-core/src/shares.rs

@@ -567,6 +567,25 @@ impl ShareStore {
         Ok(updated)
     }
 
+    /// Call a share something else. Only the name changes: the id, which the
+    /// catalog, watch state and offline files are keyed by, stays. Sync sees
+    /// the new name as a change to the share's register, like any other.
+    pub fn rename(&self, id: &str, name: &str) -> Result<Share> {
+        let name = name.trim();
+        if name.is_empty() {
+            return Err(Error::Config("a share needs a name".to_owned()));
+        }
+        let mut shares = self.list()?;
+        let share = shares
+            .iter_mut()
+            .find(|share| share.id == id)
+            .ok_or_else(|| Error::NotFound(format!("no share with id {id}")))?;
+        share.name = name.to_owned();
+        let renamed = share.clone();
+        write_json(&self.dirs.shares_file(), &shares)?;
+        Ok(renamed)
+    }
+
     /// Forget a share and its secrets.
     ///
     /// The config entry goes first here, for the mirror-image reason: if the
@@ -1257,6 +1276,25 @@ mod tests {
         );
     }
 
+    #[test]
+    fn a_renamed_share_keeps_its_id_and_refuses_an_empty_name() {
+        let (store, _) = store_in("rename");
+        let added = store
+            .add(
+                "Library",
+                "https://drive.proton.me/urls/ABC123#s3cr3t",
+                None,
+            )
+            .expect("add");
+
+        let renamed = store.rename(&added.id, "  Anime  ").expect("rename");
+        assert_eq!(renamed.id, added.id);
+        assert_eq!(renamed.name, "Anime");
+        assert_eq!(store.list().expect("list")[0].name, "Anime");
+        assert!(store.rename(&added.id, "   ").is_err());
+        assert!(store.rename("share-missing", "Anime").is_err());
+    }
+
     /// A different link is a different share. Repointing this one at it would
     /// leave every catalog row and offline file describing files that are not
     /// there.