func (h *Handler) GetProductUsage(password, productID string) (*uint, error) {
	logger := h.logger.Add("method", "GetProductUsage",
		"productID", productID)

	return h.uintFromQuery(logger, password,
		`SELECT SUM(sessions.units_used)
		   FROM offerings
		   	JOIN channels
			ON channels.offering=offerings.id
			   AND offerings.product=$1
		   	JOIN sessions
		     	ON sessions.channel=channels.id`, productID)
}
func (h *Handler) GetProductUsage(password, productID string) (*uint, error) {
	logger := h.logger.Add("method", "GetProductUsage",
		"productID", productID)

	return h.uintFromQuery(logger, password,
		`SELECT SUM(sessions.units_used)
		   FROM offerings
		   	JOIN channels
			ON channels.offering=offerings.id
			   AND offerings.product=$1
		   	JOIN sessions
		     	ON sessions.channel=channels.id`, productID)
}
func ( h * Handler ) GetProductUsage ( password , productID string ) ( * uint , error ) { logger := h . logger . Add ( " " , " " , " " , productID ) return h . uintFromQuery ( logger , password , `SELECT SUM(sessions.units_used)
		   FROM offerings
		   	JOIN channels
			ON channels.offering=offerings.id
			   AND offerings.product=$1
		   	JOIN sessions
		     	ON sessions.channel=channels.id` , productID ) }
// GetProductUsage returns total units used in all channel
// of all offerings with given product.
GetProductUsage returns total units used in all channel of all offerings with given product .