Allow approving payments in test environment

Problem/Motivation

Vipps MobilePay provides an online payment wallet. To approve payment one must open the app and confirm it. Unfortunately, access to the MT environment requires some prerequisites therefore it may slow down the adoption and cause problems for devs involved in e-commerce projects. Dependency on the app can also be problematic in automated testing environments.

Vipps MobilePay API supports approving the payment via API call which can help in these scenarios. This feature request is about implementing that support