holdings: a member of a Space publishes what they hold as room-salted album keys, sealed to the room, so "who has this" is answered while they are offline

crates/library/src/lib.rs

@@ -811,6 +811,14 @@ impl Library {
         Ok(rows.filter_map(|r| r.ok()).collect())
     }
 
+    /// Album id → MusicBrainz release id, for the albums that have one.
+    pub fn album_mbids(&self) -> Result<std::collections::BTreeMap<i64, String>> {
+        let conn = self.conn.lock().unwrap();
+        let mut stmt = conn.prepare("SELECT id, mbid FROM albums WHERE mbid IS NOT NULL AND mbid != ''")?;
+        let rows = stmt.query_map([], |r| Ok((r.get::<_, i64>(0)?, r.get::<_, String>(1)?)))?;
+        Ok(rows.filter_map(|r| r.ok()).collect())
+    }
+
     /// Per-album aggregates for the Library page: what the FILES add up to.
     /// One call for the whole library, because the page derives its stat row,
     /// its Format grouping and four of its sorts (length, size, bitrate,