add constructor for users service

src/service/users.rs

@@ -46,6 +46,13 @@ pub(crate) struct Service {
 }
 
 impl Service {
+    pub(crate) fn new(db: &'static dyn Data) -> Self {
+        Self {
+            db,
+            connections: Mutex::new(BTreeMap::new()),
+        }
+    }
+
     /// Check if a user has an account on this homeserver.
     pub(crate) fn exists(&self, user_id: &UserId) -> Result<bool> {
         self.db.exists(user_id)