refactor use stage env

[kjgarza]

Purpose

adjust service to use the staging environment addresses : https://github.com/datacite/datacite/issues/1033

Approach

I refactored all the fixtures and test as well as some default configurations to use the stage enviroment.

Open Questions and Pre-Merge TODOs

none

Learning

none

Status

• [x] Ready for Review

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)