MM-15021: Adding new builtin system schema for Guests (#10601)

* MM-15021: Adding new builtin system schema for Guests

* Fixing tests

* Setting properly the permissions

* Adding guests to sampledata

* Restrict more roles updates in the app layer for guests

* Adding comment to explain that permissions migration must go at the end

* Setting the default guest role for custom scheme during migration

* Fixing import and export

* Creating scheme guest roles on migration

* Fixing tests

* Fixing tests

* Fixing tests

app/import_validators.go

@@ -56,6 +56,12 @@ func validateSchemeImportData(data *SchemeImportData) *model.AppError {
 		}
 	}
 
+	if data.DefaultTeamGuestRole != nil {
+		if err := validateRoleImportData(data.DefaultTeamGuestRole); err != nil {
+			return err
+		}
+	}
+
 	if data.DefaultChannelAdminRole != nil {
 		if err := validateRoleImportData(data.DefaultChannelAdminRole); err != nil {
 			return err
@@ -68,6 +74,12 @@ func validateSchemeImportData(data *SchemeImportData) *model.AppError {
 		}
 	}
 
+	if data.DefaultChannelGuestRole != nil {
+		if err := validateRoleImportData(data.DefaultChannelGuestRole); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }