For #6917 (IMPORTANT) :
I am not familiar with the checkout mail from vendors after order.
Yes we can modify checkout process for clec numbers, but I think we can not bypass this checkout mail from vendors, because currently on clec page when user submit detail on activation detail page it makes an order on EN, and then it will send a request of order to the vendor.
The process will be same after modification on clec page.
Means after confirming the order from checkout page on EN, the order request for API will send by system.
And the mails may be sent by vendors when we create order on API.