Enables apps in development to be installable via the Developer sandbox

Problem Statement

If you are a developer building an Add-in for RingCentral App, there is no way to discover, and test the installation process for your add-in inside of our "Developer Sandbox" accessed through the following URL:

https://app.devtest.ringcentral.com/

Solution

Add a new area inside of the App Gallery that would allow developers to see the apps that have not yet graduated and install them into that sandbox environment so that they can be tested prior to being released publicly.