Create user story for device-roaming-status and device-reachability-status APIs

[akoshunyadi]

Problem description
For the stable release user stories are mandatory.

Expected action
Create user story files for both device-roaming-status and device-reachability-status APIs:
-> documentation/API_documentation/device-roaming-status-User-Story.md
-> documentation/API_documentation/device-reachability-status-User-Story.md

Additional context

[eric-murray]

The original proposal for the "Roaming API" can be found here.

It lists 3 possible use cases:

• For regulatory reasons, where a customer may need to be within a certain jurisdiction, or outwith others, in order for transactions to be authorised
• For security / fraud reasons, to establish that a customer is located in the country where they claim to be
• For service delivery reasons, to ensure that the customer has access to particular services, and will not incur roaming charges in accessing them

[akoshunyadi]

As part of #263 the 2 user stories have been created