added endpoint for group ownership transfer

src/services/group.js

@@ -41,6 +41,10 @@ class GroupService {
     async rename(groupId, newName) {
         await db.query("UPDATE groups SET name = $1 WHERE id = $2", [newName, groupId]).catch((e) => errorHandler(e, "groups"));;
     }
+
+    async transferOwnership(groupId, userId) {
+        await db.query("UPDATE groups SET admin_id = $1 WHERE id = $2", [userId, groupId])
+    }
 };
 
 export default new GroupService();