lib.userData: add delete

src/lib/userData.js

@@ -39,7 +39,26 @@ function getUserData(id, key, fallback = null) {
   });
 }
 
+function deleteUserData(id, key) {
+  return new Promise((resolve, reject) => {
+    hf.database.run(
+      "DELETE FROM user_data WHERE key = $key",
+      {
+        $key: `${id}[${key}]`,
+      },
+      (err) => {
+        if (err == null) {
+          resolve(true);
+        } else {
+          reject(err);
+        }
+      }
+    );
+  });
+}
+
 module.exports = {
   setUserData,
   getUserData,
+  deleteUserData,
 };