MM-25263 Add group members to search and get users and create getGroupStats endpoint (#14733)

Add tests for SearchInGroup

app/app_iface.go

@@ -541,6 +541,7 @@ type AppIface interface {
 	GetGroupByName(name string, opts model.GroupSearchOpts) (*model.Group, *model.AppError)
 	GetGroupByRemoteID(remoteID string, groupSource model.GroupSource) (*model.Group, *model.AppError)
 	GetGroupChannel(userIds []string) (*model.Channel, *model.AppError)
+	GetGroupMemberCount(groupID string) (int64, *model.AppError)
 	GetGroupMemberUsers(groupID string) ([]*model.User, *model.AppError)
 	GetGroupMemberUsersPage(groupID string, page int, perPage int) ([]*model.User, int, *model.AppError)
 	GetGroupSyncable(groupID string, syncableID string, syncableType model.GroupSyncableType) (*model.GroupSyncable, *model.AppError)
@@ -836,6 +837,7 @@ type AppIface interface {
 	SearchUserAccessTokens(term string) ([]*model.UserAccessToken, *model.AppError)
 	SearchUsers(props *model.UserSearch, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
 	SearchUsersInChannel(channelId string, term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
+	SearchUsersInGroup(groupID string, term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
 	SearchUsersInTeam(teamId, term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
 	SearchUsersNotInChannel(teamId string, channelId string, term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)
 	SearchUsersNotInTeam(notInTeamId string, term string, options *model.UserSearchOptions) ([]*model.User, *model.AppError)