API enhancement - Line Eligibility

[jgarciahospital]

(As discussed in API backlog camaraproject/APIBacklog#94)

Problem description

As scope enhancement for current Carrier Billing CheckOut API, this mechanism will allow 3rd party applications (known as merchants in Carrier Billing services) to validate the eligibility of the telco's subscribers before the actual service is triggered, improving user experience.

Expected action

Analyze and include the eligibility functionality into the Carrier Billing Checkout service (as new feature/endpoint or new API)