Adding saml migration command (#8263)

* Adding saml migration command

* Texts fixed

einterfaces/account_migration.go

@@ -6,5 +6,6 @@ package einterfaces
 import "github.com/mattermost/mattermost-server/model"
 
 type AccountMigrationInterface interface {
-	MigrateToLdap(fromAuthService string, forignUserFieldNameToMatch string, force bool) *model.AppError
+	MigrateToLdap(fromAuthService string, forignUserFieldNameToMatch string, force bool, dryRun bool) *model.AppError
+	MigrateToSaml(fromAuthService string, usersMap map[string]string, auto bool, dryRun bool) *model.AppError
 }