code: @NotNull
      @ObjectiveCName("inviteMemberPromiseWithGid:withUid:")
      public Promise<Void> inviteMemberPromise(int gid, int uid) {
          return modules.getGroupsModule().addMember(gid, uid);
      }
docs: Adding member to group
  
  @param gid group's id
  @param uid user's id
  @return promise of adding member to group