added new endpoint

src/controllers/group.js

@@ -65,6 +65,14 @@ class GroupController {
 
         return res.status(200).send(result);
     }
+
+    async getAdminId(req, res) {
+        const groupId = req.params.groupId;
+
+        let result = await GroupService.getAdminId(groupId);
+
+        return res.status(200).send(result.toString())
+    }
 }
 
 export default new GroupController();