Add workflow for staging nginx

[katjuell]

Description

Fix workflow to use different Nginx config files for staging and prod.

Test process

Auth should work everywhere.

Requirements to merge

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code in hard-to-understand areas
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes