[Backend] Fixed case routes

[amlannandy]

Description

1. Fixed the open case, open folder routes to return data in JSON-friendly format.
2. Fixed the file path to work with all systems.

Fixes #149

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Demo video attached.

Test Configuration:

• Ubuntu 20.04.1

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules