BAU: ConfigurationService Consistency Improvements

[BenjaminWCO]

What

• Added helper functions in Config Service for common patterns for flags and URIs.
• Config Service consistently returns URI objects rather than a mix of strings and URIs.
• URI environment variables no longer default to empty when when missing -will throw instead - this behaviour seemed to be relied on in tests only.
• More consistent method names in Config Service.

How to review

Code Review

Checklist

• Impact on orch and auth mutual dependencies has been checked.