Use keptn/go-utils to access Keptn APIs

[arthurpitman]

Currently the dynatrace-service contains some implementations for accessing for some Keptn APIs.

Instead, it should use the clients provided by keptn/go-utils

e.g. func (a *APIHandler) CreateService(project string, service models.CreateService) (string, *models.Error)

should be used to provide the implementation in

dynatrace-service/internal/keptn/keptn_service_client.go

Lines 59 to 70 in 9cab34c

	func (c *ServiceClient) CreateServiceInProject(project string, service string) error {
	serviceModel := &apimodels.CreateService{
	ServiceName: &service,
	}
	reqBody, err := json.Marshal(serviceModel)
	if err != nil {
	return fmt.Errorf("could not marshal service payload: %s", err.Error())
	}
	_, err = c.apiClient.Post(getServicePathFor(project), reqBody)
	return err
	}