add prototype of highscore list

src/model/highscore.rs

@@ -0,0 +1,28 @@
+use crate::Backend;
+
+pub(crate) struct Rank {
+    pub(crate) name: Option<String>,
+    pub(crate) uuid: String,
+    pub(crate) amount: i64,
+}
+
+impl Backend {
+    pub(crate) async fn highscore(&self) -> Vec<Rank> {
+        match self {
+            Backend::Sqlite(db) => sqlx::query_as!(
+                Rank,
+                "SELECT 
+                    c.name,
+                    c.uuid,
+                    COUNT(s.client_uuid) as amount
+                FROM client c
+                LEFT JOIN sightings s ON c.uuid = s.client_uuid
+                GROUP BY c.uuid, c.name
+                ORDER BY amount DESC"
+            )
+            .fetch_all(db)
+            .await
+            .unwrap_or_default(),
+        }
+    }
+}