Method to get the HTML and text rendered version of a trigger.
https://api.wbsrvc.com/Trigger/GetEmailMessage/
POST
| user_key Required |
User Key of the user who initiates the call. Type: string |
| trigger_id Required |
ID of the trigger. Type: integer |
| client_id Optional |
Client ID of the client in which the trigger is located. Type: integer |