Missing CognitoEventUserPoolsPreTokenGeneration request and response types

[cloudlena]

The Cognito User Pools event type for Pre Token Generation is missing.

I guess it should be something like

// CognitoEventUserPoolsPreTokenGeneration is sent by AWS Cognito User Pools before a user's token is generated.
type CognitoEventUserPoolsPreTokenGeneration struct {
	CognitoEventUserPoolsHeader
	Request  CognitoEventUserPoolsPreTokenGenerationRequest  `json:"request"`
	Response CognitoEventUserPoolsPreTokenGenerationResponse `json:"response"`
}

// CognitoEventUserPoolsPreTokenGenerationRequest contains the request portion of a PreTokenGeneration event.
type CognitoEventUserPoolsPreTokenGenerationRequest struct {
	UserAttributes     map[string]string                        `json:"userAttributes"`
	GroupConfiguration CognitoEventsUserPoolsGroupConfiguration `json:"groupConfiguration"`
}

// CognitoEventUserPoolsPreTokenGenerationResponse contains the response portion of a PreTokenGeneration event.
type CognitoEventUserPoolsPreTokenGenerationResponse struct {
	ClaimsOverrideDetails CognitoEventsUserPoolsClaimsOverrideDetails `json:"claimsOverrideDetails"`
}

// CognitoEventsUserPoolsClaimsOverrideDetails is the claims override details
// part of a Cognito event.
type CognitoEventsUserPoolsClaimsOverrideDetails struct {
	ClaimsToAddOrOverride map[string]string                        `json:"claimsToAddOrOverride"`
	ClaimsToSuppress      []string                                 `json:"claimsToSuppress"`
	GroupOverrideDetails  CognitoEventsUserPoolsGroupConfiguration `json:"groupOverrideDetails"`
}

// CognitoEventsUserPoolsGroupConfiguration is the group configuration part of
// a Cognito event.
type CognitoEventsUserPoolsGroupConfiguration struct {
	GroupsToOverride   []string `json:"groupsToOverride"`
	IAMRolesToOverride []string `json:"iamRolesToOverride"`
	PreferredRole      string   `json:"preferredRole"`
}

Is that correct? The JSON in the docs doesn't appear to be valid so I had to do some guesswork. If it's correct, I can make a PR to add them.

[bmoffatt]

These types have been added by #95