Missing field enableSMSMFA on struct events.CognitoEventUserPoolsMigrateUserResponse

[andresherreram]

Is your feature request related to a problem? Please describe.
According to cognito migrate user lambda trigger documentation the event struct could use a field called enableSMSMFA to allow force the migrated user to trigger the SMSMFA step.

That field is not present in the current events package.

Describe the solution you'd like
On file events/cognito.go:

// CognitoEventUserPoolsMigrateUserResponse contains the response portion of a MigrateUser event
type CognitoEventUserPoolsMigrateUserResponse struct {
	UserAttributes         map[string]string `json:"userAttributes"`
	FinalUserStatus        string            `json:"finalUserStatus"`
	MessageAction          string            `json:"messageAction"`
	DesiredDeliveryMediums []string          `json:"desiredDeliveryMediums"`
	ForceAliasCreation     bool              `json:"forceAliasCreation"`
	EnableSMSMFA           bool              `json:"enableSMSMFA"`
}

Describe alternatives you've considered
For now I'm trying to create a local struct that inlude the original plus that field:

type	UserMigrationEventResponse struct {
	events.CognitoEventUserPoolsMigrateUserResponse
	EnableSMSMFA bool `json:"enableSMSMFA"`
}

type UserMigrateAuthEvent struct {
	events.CognitoEventUserPoolsHeader
	events.CognitoEventUserPoolsMigrateUserRequest `json:"request"`
	UserMigrationEventResponse                     `json:"response"`
}

Additional context
Documentation of the event: https://docs.aws.amazon.com/cognito/latest/developerguide/user-pool-lambda-migrate-user.html#cognito-user-pools-lambda-trigger-syntax-user-migration