Migrating Team.SaveMember/SaveMultipleMembers into errors (#14924)

* Migrating Team.SaveMember/SaveMultipleMembers into errors

* Removing copy/paste comments

* Fixing another small thing

* Fixing tests

* Addressing PR review comments

* Fixing some tests

* Fixing golangci-lint

* Fixing linter

* Regenerating store layers

* Fix lint error after merge

* Other lint error fixed

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

store/searchlayer/team_layer.go

@@ -13,7 +13,7 @@ type SearchTeamStore struct {
 	rootStore *SearchStore
 }
 
-func (s SearchTeamStore) SaveMember(teamMember *model.TeamMember, maxUsersPerTeam int) (*model.TeamMember, *model.AppError) {
+func (s SearchTeamStore) SaveMember(teamMember *model.TeamMember, maxUsersPerTeam int) (*model.TeamMember, error) {
 	member, err := s.TeamStore.SaveMember(teamMember, maxUsersPerTeam)
 	if err == nil {
 		s.rootStore.indexUserFromID(member.UserId)