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>

app/import_functions.go

@@ -754,9 +754,22 @@ func (a *App) importUserTeams(user *model.User, data *[]UserTeamImportData) *mod
 
 	newMembers := []*model.TeamMember{}
 	if len(newTeamMembers) > 0 {
-		newMembers, err = a.Srv().Store.Team().SaveMultipleMembers(newTeamMembers, *a.Config().TeamSettings.MaxUsersPerTeam)
-		if err != nil {
-			return err
+		var nErr error
+		newMembers, nErr = a.Srv().Store.Team().SaveMultipleMembers(newTeamMembers, *a.Config().TeamSettings.MaxUsersPerTeam)
+		if nErr != nil {
+			var appErr *model.AppError
+			var conflictErr *store.ErrConflict
+			var limitExeededErr *store.ErrLimitExceeded
+			switch {
+			case errors.As(nErr, &appErr): // in case we haven't converted to plain error.
+				return appErr
+			case errors.As(nErr, &conflictErr):
+				return model.NewAppError("BulkImport", "app.import.import_user_teams.save_members.conflict.app_error", nil, nErr.Error(), http.StatusBadRequest)
+			case errors.As(nErr, &limitExeededErr):
+				return model.NewAppError("BulkImport", "app.import.import_user_teams.save_members.max_accounts.app_error", nil, nErr.Error(), http.StatusBadRequest)
+			default: // last fallback in case it doesn't map to an existing app error.
+				return model.NewAppError("BulkImport", "app.import.import_user_teams.save_members.error", nil, nErr.Error(), http.StatusInternalServerError)
+			}
 		}
 	}