Exercise => Add correction fields

models/Exercise.ts

 import GitlabRepository from '../../shared/types/Gitlab/GitlabRepository';
+import { CommitSchema } from '@gitbeaker/rest';
+import User             from './User';
+import Assignment       from './Assignment';
 
 
 interface Exercise {
@@ -10,6 +13,12 @@ interface Exercise {
     gitlabCreationInfo: GitlabRepository;
     gitlabLastInfo: GitlabRepository;
     gitlabLastInfoDate: string;
+
+    members: Array<User> | undefined;
+    assignment: Assignment | undefined;
+
+    isCorrection: boolean;
+    correctionCommit: CommitSchema | undefined;
 }