Create a new sub-module for Transactional Messaging calls.

See https://developer.salesforce.com/docs/atlas.en-us.mc-apis.meta/mc-apis/r...

Create a new sub-module called marketing_cloud_transactional_messaging to expose services for the following calls:

POST /messaging/v1/sms/messages/ https://developer.salesforce.com/docs/#detail_sendSMSMessageMultipleReci...
POST /messaging/v1/email/messages/ https://developer.salesforce.com/docs/#detail_sendMessageMultipleRecipients
POST /messaging/v1/sms/definitions https://developer.salesforce.com/docs/#detail_createSMSSendDefinition
GET /messaging/v1/sms/definitions https://developer.salesforce.com/docs/#detail_getSMSDefinitions
POST /messaging/v1/email/definitions https://developer.salesforce.com/docs/#detail_createSendDefinition
GET /messaging/v1/email/definitions https://developer.salesforce.com/docs/#detail_getDefinitions
POST /messaging/v1/sms/messages/{messageKey} https://developer.salesforce.com/docs/#detail_sendSMSMessageSingleRecipient
GET /messaging/v1/sms/messages/{messageKey} https://developer.salesforce.com/docs/#detail_getSMSSendStatusForRecipient
GET /messaging/v1/sms/messages/?type=notSent https://developer.salesforce.com/docs/#detail_getSMSMessagesNotSent
POST /messaging/v1/email/messages/{messageKey} https://developer.salesforce.com/docs/#detail_sendMessageSingleRecipient
GET /messaging/v1/email/messages/{messageKey} https://developer.salesforce.com/docs/#detail_getSendStatusForRecipient
GET /messaging/v1/email/messages/?type=notSent https://developer.salesforce.com/docs/#detail_getMessagesNotSent
GET /messaging/v1/sms/definitions/{definitionKey} https://developer.salesforce.com/docs/#detail_getSMSSendDefinition
PATCH /messaging/v1/sms/definitions/{definitionKey} https://developer.salesforce.com/docs/#detail_updateSMSMessageDefinition
DELETE /messaging/v1/sms/definitions/{definitionKey} https://developer.salesforce.com/docs/#detail_deleteSMSMessageDefinition
GET /messaging/v1/email/definitions/{definitionKey} https://developer.salesforce.com/docs/#detail_getSendDefinition
PATCH /messaging/v1/email/definitions/{definitionKey} https://developer.salesforce.com/docs/#detail_updateMessageDefinition
DELETE /messaging/v1/email/definitions/{definitionKey} https://developer.salesforce.com/docs/#detail_deleteMessageDefinition
GET /messaging/v1/sms/definitions/{definitionKey}/queue https://developer.salesforce.com/docs/#detail_getSMSQueueMetricsForDefin...
DELETE /messaging/v1/sms/definitions/{definitionKey}/queue https://developer.salesforce.com/docs/#detail_deleteSMSQueuedMessagesFor...
GET /messaging/v1/email/definitions/{definitionKey}/queue https://developer.salesforce.com/docs/#detail_getQueueMetricsForDefinition
DELETE /messaging/v1/email/definitions/{definitionKey}/queue https://developer.salesforce.com/docs/#detail_deleteQueuedMessagesForDef...