groupServiceConfig: { // optional
interface CsGroupService {
medium: string | string[],
gradeLevel: string | string[],
subject: string | string[],
config?: CsGroupServiceConfig
deleteById(id: string, config?: CsGroupServiceConfig): Observable<void>;
getAll(config?: CsGroupServiceConfig): Observable<Group[]>;
getById(id: string, config?: CsGroupServiceConfig): Observable<Group>;
addMemberById(memberId: string, groupId: string, config?: CsGroupServiceConfig): Observable<Group>;
removeMemberById(memberId: string, groupId: string, config?: CsGroupServiceConfig): Observable<void>;