code: public MailRequest newTextTemplateMailRequest(String subjectTemplate, String textTemplateName, Map<String, Object> parameters) {
          return createTemplateMailRequest(generateRequestId(), subjectTemplate, textTemplateName, false, parameters);
      }
docs: Creates a MailRequest from the specified template.
  The request id is automatically generated.
  
  @param subjectTemplate  a string that uses the parameters & TemplateEngine to interpolate values
  @param textTemplateName the name of the classpath template resource
  @param parameters
  @return a text mail request